Saturday 20 August 2016
Scarlet colored beast of revelation 17:The watchtower Society's commentary.
What Is the Scarlet-Colored Beast of Revelation Chapter 17?
Keys to identifying the scarlet-colored beast
A political entity. The scarlet-colored beast has “seven heads” that are said to represent “seven mountains” and “seven kings,” or ruling powers. (Revelation 17:9, 10) Mountains and beasts are used in the Bible as symbols of governments.—Jeremiah 51:24, 25; Daniel 2:44, 45; 7:17, 23.
A likeness of the worldwide political system. The scarlet-colored beast resembles the seven-headed beast of Revelation chapter 13, which represents the worldwide political system. Both beasts have seven heads, ten horns, and blasphemous names. (Revelation 13:1; 17:3) These similarities are too striking to be a coincidence. The scarlet-colored beast is an image, or likeness, of the worldwide political system.—Revelation 13:15.
Power from other rulerships. The scarlet-colored beast “springs from,” or owes its existence to, other ruling forces.—Revelation 17:11, 17.
Linked with religion. Babylon the Great, the world’s collective body of false religions, sits on the scarlet-colored beast, showing that the beast is influenced by religious groups.—Revelation 17:3-5.
Dishonors God. The beast is “full of blasphemous names.”—Revelation 17:3.
Temporarily inactive. The scarlet-colored beast would be in “the abyss,” * or inactive, for a time but would rise again.—Revelation 17:8.
Bible prophecy fulfilled
Consider how the United Nations and its predecessor, the League of Nations, have fulfilled the Bible’s prophecy of the scarlet-colored beast.
A political entity.:The United Nations supports the political system by upholding “the sovereign equality of all its Members.”
A likeness of the worldwide political system.:In 2011, the United Nations added its 193rd member state. Thus, it claims to represent the vast majority of nations and peoples in the world.
Power from other rulerships.:The United Nations owes its existence to its member nations and has only as much power and authority as they grant to it.
Linked with religion.:Both the League of Nations and the United Nations have consistently received the backing of the world’s religions.
Dishonors God. :The United Nations was established “to maintain international peace and security.” * While this goal might seem to be praiseworthy, the UN actually dishonors God by claiming to do what he has said only his Kingdom will accomplish.—Psalm 46:9; Daniel 2:44.
Temporarily inactive.:The League of Nations, which was formed shortly after World War I to maintain peace, was unable to prevent international aggression. It ceased to function when World War II began in 1939. In 1945, after World War II ended, the United Nations was formed. Its purposes, methods, and structure closely resemble those of the League of Nations.
Keys to identifying the scarlet-colored beast
A political entity. The scarlet-colored beast has “seven heads” that are said to represent “seven mountains” and “seven kings,” or ruling powers. (Revelation 17:9, 10) Mountains and beasts are used in the Bible as symbols of governments.—Jeremiah 51:24, 25; Daniel 2:44, 45; 7:17, 23.
A likeness of the worldwide political system. The scarlet-colored beast resembles the seven-headed beast of Revelation chapter 13, which represents the worldwide political system. Both beasts have seven heads, ten horns, and blasphemous names. (Revelation 13:1; 17:3) These similarities are too striking to be a coincidence. The scarlet-colored beast is an image, or likeness, of the worldwide political system.—Revelation 13:15.
Power from other rulerships. The scarlet-colored beast “springs from,” or owes its existence to, other ruling forces.—Revelation 17:11, 17.
Linked with religion. Babylon the Great, the world’s collective body of false religions, sits on the scarlet-colored beast, showing that the beast is influenced by religious groups.—Revelation 17:3-5.
Dishonors God. The beast is “full of blasphemous names.”—Revelation 17:3.
Temporarily inactive. The scarlet-colored beast would be in “the abyss,” * or inactive, for a time but would rise again.—Revelation 17:8.
Bible prophecy fulfilled
Consider how the United Nations and its predecessor, the League of Nations, have fulfilled the Bible’s prophecy of the scarlet-colored beast.
A political entity.:The United Nations supports the political system by upholding “the sovereign equality of all its Members.”
A likeness of the worldwide political system.:In 2011, the United Nations added its 193rd member state. Thus, it claims to represent the vast majority of nations and peoples in the world.
Power from other rulerships.:The United Nations owes its existence to its member nations and has only as much power and authority as they grant to it.
Linked with religion.:Both the League of Nations and the United Nations have consistently received the backing of the world’s religions.
Dishonors God. :The United Nations was established “to maintain international peace and security.” * While this goal might seem to be praiseworthy, the UN actually dishonors God by claiming to do what he has said only his Kingdom will accomplish.—Psalm 46:9; Daniel 2:44.
Temporarily inactive.:The League of Nations, which was formed shortly after World War I to maintain peace, was unable to prevent international aggression. It ceased to function when World War II began in 1939. In 1945, after World War II ended, the United Nations was formed. Its purposes, methods, and structure closely resemble those of the League of Nations.
The Watchtower Society's commentary on "Faith"
FAITH:
The word “faith” is translated from the Greek piʹstis, primarily conveying the thought of confidence, trust, firm persuasion. Depending on the context, the Greek word may also be understood to mean “faithfulness” or “fidelity.”—1Th 3:7; Tit 2:10.
The Scriptures tell us: “Faith is the assured expectation of things hoped for, the evident demonstration of realities though not beheld.” (Heb 11:1) “Assured expectation” translates the Greek word hy·poʹsta·sis. This term is common in ancient papyrus business documents. It conveys the idea of something that underlies visible conditions and guarantees a future possession. In view of this, Moulton and Milligan suggest the rendering: “Faith is the title deed of things hoped for.” (Vocabulary of the Greek Testament, 1963, p. 660) The Greek word eʹleg·khos, rendered “evident demonstration,” conveys the idea of bringing forth evidence that demonstrates something, particularly something contrary to what appears to be the case. Thereby this evidence makes clear what has not been discerned before and so refutes what has only appeared to be the case. “The evident demonstration,” or evidence for conviction, is so positive or powerful that faith is said to be it.
Faith is, therefore, the basis for hope and the evidence for conviction concerning unseen realities. The entire body of truths delivered by Jesus Christ and his inspired disciples constitutes the true Christian “faith.” (Joh 18:37; Ga 1:7-9; Ac 6:7; 1Ti 5:8) Christian faith is based on the complete Word of God, including the Hebrew Scriptures, to which Jesus and the writers of the Christian Greek Scriptures frequently referred in support of their statements.
Faith is based on concrete evidence. The visible creative works testify to the existence of an invisible Creator. (Ro 1:20) The actual occurrences taking place during the ministry and earthly life of Jesus Christ identify him as the Son of God. (Mt 27:54; see JESUS CHRIST.) God’s record of providing for his earthly creatures serves as a valid basis for believing that he will surely provide for his servants, and his record as a Giver and Restorer of life lends ample evidence to the credibility of the resurrection hope. (Mt 6:26, 30, 33; Ac 17:31; 1Co 15:3-8, 20, 21) Furthermore, the reliability of God’s Word and the accurate fulfillment of its prophecies instill confidence in the realization of all of His promises. (Jos 23:14) Thus, in these many ways, “faith follows the thing heard.”—Ro 10:17; compare Joh 4:7-30, 39-42; Ac 14:8-10.
So faith is not credulity. The person who may ridicule faith usually has faith himself in tried and trusted friends. The scientist has faith in the principles of his branch of science. He bases new experiments on past discoveries and looks for new discoveries on the basis of those things already established as true. Likewise, the farmer prepares his soil and sows the seed, expecting, as in previous years, that the seed will sprout and that the plants will grow as they receive the needed moisture and sunshine. Therefore faith in the stability of the natural laws governing the universe actually constitutes a foundation for man’s plans and activities. Such stability is alluded to by the wise writer of Ecclesiastes: “The sun also has flashed forth, and the sun has set, and it is coming panting to its place where it is going to flash forth. The wind is going to the south, and it is circling around to the north. Round and round it is continually circling, and right back to its circlings the wind is returning. All the winter torrents are going forth to the sea, yet the sea itself is not full. To the place where the winter torrents are going forth, there they are returning so as to go forth.”—Ec 1:5-7.
In the Hebrew Scriptures, the word ʼa·manʹ and other words closely related convey the sense of trustworthiness, faithfulness, steadiness, steadfastness, being firmly established, long-lasting. (Ex 17:12; De 28:59; 1Sa 2:35; 2Sa 7:16; Ps 37:3) One related noun (ʼemethʹ) usually denotes “truth,” but also “faithfulness” or “trustworthiness.” (2Ch 15:3, ftn; 2Sa 15:20; compare Ne 7:2, ftn.) The familiar term “Amen” (Heb., ʼa·menʹ) also comes from ʼa·manʹ.—See AMEN.
Ancient Examples of Faith. Each one of the “so great a cloud of witnesses” mentioned by Paul (Heb 12:1) had a valid basis for faith. For example, Abel certainly knew about God’s promise concerning a “seed” that would bruise “the serpent” in the head. And he saw tangible evidences of the fulfillment of the sentence Jehovah pronounced upon his parents in Eden. Outside Eden, Adam and his family ate bread in the sweat of their face because the ground was cursed and, therefore, produced thorns and thistles. Likely Abel observed that Eve’s craving was for her husband and that Adam dominated his wife. Undoubtedly his mother commented about the pain attending her pregnancy. Then, too, the entrance to the garden of Eden was being guarded by cherubs and the flaming blade of a sword. (Ge 3:14-19, 24) All of this constituted an “evident demonstration,” giving Abel the assurance that deliverance would come through the ‘seed of promise.’ Therefore, prompted by faith, he “offered God a sacrifice,” one that proved to be of greater worth than that of Cain.—Heb 11:1, 4.
Abraham had a firm basis for faith in a resurrection, for he and Sarah had experienced the miraculous restoration of their reproductive powers, which was, in a sense, comparable to a resurrection, allowing Abraham’s family line to continue through Sarah. Isaac was born as the result of this miracle. When told to offer up Isaac, Abraham had faith that God would resurrect his son. He based such faith on God’s promise: “It is by means of Isaac that what will be called your seed will be.”—Ge 21:12; Heb 11:11, 12, 17-19.
Evidence for genuine conviction was also involved in the case of those who came to or who were brought to Jesus to be healed. Even if not eyewitnesses personally, they at least had heard about Jesus’ powerful works. Then, on the basis of what they saw or heard, they concluded that Jesus could heal them also. Moreover, they were acquainted with God’s Word and thus were familiar with the miracles performed by the prophets in times past. Upon hearing Jesus, some concluded that he was “The Prophet,” and others that he was “the Christ.” In view of this, it was most fitting for Jesus on occasion to say to those who were healed, “Your faith has made you well.” Had those persons not exercised faith in Jesus, they would not have approached him in the first place and, therefore, would not have received healing for themselves.—Joh 7:40, 41; Mt 9:22; Lu 17:19.
Likewise, the great faith of the army officer who entreated Jesus in behalf of his manservant rested on evidence, on the basis of which he concluded that Jesus’ merely ‘saying the word’ would result in the healing of his manservant. (Mt 8:5-10, 13) However, we note that Jesus healed all who came to him, not requiring faith greater or less according to their disease, nor failing to heal any of these with the excuse that he could not do it because their faith was not strong enough. Jesus performed these healings as a witness, to establish faith. In his home territory, where much unfaithfulness was expressed, he chose not to perform many powerful works, not because of inability, but because the people refused to listen and were unworthy.—Mt 13:58.
Christian Faith. To be acceptable to God, it is now necessary for one to exercise faith in Jesus Christ, and this makes possible a righteous standing with God. (Ga 2:16) Those lacking such faith are rejected by Jehovah.—Joh 3:36; compare Heb 11:6.
Faith is not the possession of all persons, as it is a fruit of God’s spirit. (2Th 3:2; Ga 5:22) And a Christian’s faith is not static, but it grows. (2Th 1:3) Hence, the request of Jesus’ disciples, “Give us more faith,” was very appropriate, and he did provide them the foundation for increased faith. He supplied them with greater evidence and understanding on which to base their faith.—Lu 17:5.
The entire life course of a Christian is actually governed by faith, enabling him to overcome mountainlike obstacles that would hinder his service to God. (2Co 5:7; Mt 21:21, 22) Additionally, there must be works consistent with and in display of faith, but works of the Mosaic Law are not required. (Jas 2:21-26; Ro 3:20) Trials can strengthen faith. Faith serves as a protective shield in the Christian’s spiritual warfare, helping him to overcome the Devil and be a conqueror of the world.—1Pe 1:6, 7; Eph 6:16; 1Pe 5:9; 1Jo 5:4.
But faith cannot be taken for granted, because lack of faith is ‘the sin that so easily entangles one.’ To maintain a firm faith requires putting up a hard fight for it, resisting men who could plunge one into immorality, combating the works of the flesh, avoiding the snare of materialism, shunning faith-destroying philosophies and traditions of men, and, above all, looking “intently at the Chief Agent and Perfecter of our faith, Jesus.”—Heb 12:1, 2; Jude 3, 4; Ga 5:19-21; 1Ti 6:9, 10; Col 2:8.
The word “faith” is translated from the Greek piʹstis, primarily conveying the thought of confidence, trust, firm persuasion. Depending on the context, the Greek word may also be understood to mean “faithfulness” or “fidelity.”—1Th 3:7; Tit 2:10.
The Scriptures tell us: “Faith is the assured expectation of things hoped for, the evident demonstration of realities though not beheld.” (Heb 11:1) “Assured expectation” translates the Greek word hy·poʹsta·sis. This term is common in ancient papyrus business documents. It conveys the idea of something that underlies visible conditions and guarantees a future possession. In view of this, Moulton and Milligan suggest the rendering: “Faith is the title deed of things hoped for.” (Vocabulary of the Greek Testament, 1963, p. 660) The Greek word eʹleg·khos, rendered “evident demonstration,” conveys the idea of bringing forth evidence that demonstrates something, particularly something contrary to what appears to be the case. Thereby this evidence makes clear what has not been discerned before and so refutes what has only appeared to be the case. “The evident demonstration,” or evidence for conviction, is so positive or powerful that faith is said to be it.
Faith is, therefore, the basis for hope and the evidence for conviction concerning unseen realities. The entire body of truths delivered by Jesus Christ and his inspired disciples constitutes the true Christian “faith.” (Joh 18:37; Ga 1:7-9; Ac 6:7; 1Ti 5:8) Christian faith is based on the complete Word of God, including the Hebrew Scriptures, to which Jesus and the writers of the Christian Greek Scriptures frequently referred in support of their statements.
Faith is based on concrete evidence. The visible creative works testify to the existence of an invisible Creator. (Ro 1:20) The actual occurrences taking place during the ministry and earthly life of Jesus Christ identify him as the Son of God. (Mt 27:54; see JESUS CHRIST.) God’s record of providing for his earthly creatures serves as a valid basis for believing that he will surely provide for his servants, and his record as a Giver and Restorer of life lends ample evidence to the credibility of the resurrection hope. (Mt 6:26, 30, 33; Ac 17:31; 1Co 15:3-8, 20, 21) Furthermore, the reliability of God’s Word and the accurate fulfillment of its prophecies instill confidence in the realization of all of His promises. (Jos 23:14) Thus, in these many ways, “faith follows the thing heard.”—Ro 10:17; compare Joh 4:7-30, 39-42; Ac 14:8-10.
So faith is not credulity. The person who may ridicule faith usually has faith himself in tried and trusted friends. The scientist has faith in the principles of his branch of science. He bases new experiments on past discoveries and looks for new discoveries on the basis of those things already established as true. Likewise, the farmer prepares his soil and sows the seed, expecting, as in previous years, that the seed will sprout and that the plants will grow as they receive the needed moisture and sunshine. Therefore faith in the stability of the natural laws governing the universe actually constitutes a foundation for man’s plans and activities. Such stability is alluded to by the wise writer of Ecclesiastes: “The sun also has flashed forth, and the sun has set, and it is coming panting to its place where it is going to flash forth. The wind is going to the south, and it is circling around to the north. Round and round it is continually circling, and right back to its circlings the wind is returning. All the winter torrents are going forth to the sea, yet the sea itself is not full. To the place where the winter torrents are going forth, there they are returning so as to go forth.”—Ec 1:5-7.
In the Hebrew Scriptures, the word ʼa·manʹ and other words closely related convey the sense of trustworthiness, faithfulness, steadiness, steadfastness, being firmly established, long-lasting. (Ex 17:12; De 28:59; 1Sa 2:35; 2Sa 7:16; Ps 37:3) One related noun (ʼemethʹ) usually denotes “truth,” but also “faithfulness” or “trustworthiness.” (2Ch 15:3, ftn; 2Sa 15:20; compare Ne 7:2, ftn.) The familiar term “Amen” (Heb., ʼa·menʹ) also comes from ʼa·manʹ.—See AMEN.
Ancient Examples of Faith. Each one of the “so great a cloud of witnesses” mentioned by Paul (Heb 12:1) had a valid basis for faith. For example, Abel certainly knew about God’s promise concerning a “seed” that would bruise “the serpent” in the head. And he saw tangible evidences of the fulfillment of the sentence Jehovah pronounced upon his parents in Eden. Outside Eden, Adam and his family ate bread in the sweat of their face because the ground was cursed and, therefore, produced thorns and thistles. Likely Abel observed that Eve’s craving was for her husband and that Adam dominated his wife. Undoubtedly his mother commented about the pain attending her pregnancy. Then, too, the entrance to the garden of Eden was being guarded by cherubs and the flaming blade of a sword. (Ge 3:14-19, 24) All of this constituted an “evident demonstration,” giving Abel the assurance that deliverance would come through the ‘seed of promise.’ Therefore, prompted by faith, he “offered God a sacrifice,” one that proved to be of greater worth than that of Cain.—Heb 11:1, 4.
Abraham had a firm basis for faith in a resurrection, for he and Sarah had experienced the miraculous restoration of their reproductive powers, which was, in a sense, comparable to a resurrection, allowing Abraham’s family line to continue through Sarah. Isaac was born as the result of this miracle. When told to offer up Isaac, Abraham had faith that God would resurrect his son. He based such faith on God’s promise: “It is by means of Isaac that what will be called your seed will be.”—Ge 21:12; Heb 11:11, 12, 17-19.
Evidence for genuine conviction was also involved in the case of those who came to or who were brought to Jesus to be healed. Even if not eyewitnesses personally, they at least had heard about Jesus’ powerful works. Then, on the basis of what they saw or heard, they concluded that Jesus could heal them also. Moreover, they were acquainted with God’s Word and thus were familiar with the miracles performed by the prophets in times past. Upon hearing Jesus, some concluded that he was “The Prophet,” and others that he was “the Christ.” In view of this, it was most fitting for Jesus on occasion to say to those who were healed, “Your faith has made you well.” Had those persons not exercised faith in Jesus, they would not have approached him in the first place and, therefore, would not have received healing for themselves.—Joh 7:40, 41; Mt 9:22; Lu 17:19.
Likewise, the great faith of the army officer who entreated Jesus in behalf of his manservant rested on evidence, on the basis of which he concluded that Jesus’ merely ‘saying the word’ would result in the healing of his manservant. (Mt 8:5-10, 13) However, we note that Jesus healed all who came to him, not requiring faith greater or less according to their disease, nor failing to heal any of these with the excuse that he could not do it because their faith was not strong enough. Jesus performed these healings as a witness, to establish faith. In his home territory, where much unfaithfulness was expressed, he chose not to perform many powerful works, not because of inability, but because the people refused to listen and were unworthy.—Mt 13:58.
Christian Faith. To be acceptable to God, it is now necessary for one to exercise faith in Jesus Christ, and this makes possible a righteous standing with God. (Ga 2:16) Those lacking such faith are rejected by Jehovah.—Joh 3:36; compare Heb 11:6.
Faith is not the possession of all persons, as it is a fruit of God’s spirit. (2Th 3:2; Ga 5:22) And a Christian’s faith is not static, but it grows. (2Th 1:3) Hence, the request of Jesus’ disciples, “Give us more faith,” was very appropriate, and he did provide them the foundation for increased faith. He supplied them with greater evidence and understanding on which to base their faith.—Lu 17:5.
The entire life course of a Christian is actually governed by faith, enabling him to overcome mountainlike obstacles that would hinder his service to God. (2Co 5:7; Mt 21:21, 22) Additionally, there must be works consistent with and in display of faith, but works of the Mosaic Law are not required. (Jas 2:21-26; Ro 3:20) Trials can strengthen faith. Faith serves as a protective shield in the Christian’s spiritual warfare, helping him to overcome the Devil and be a conqueror of the world.—1Pe 1:6, 7; Eph 6:16; 1Pe 5:9; 1Jo 5:4.
But faith cannot be taken for granted, because lack of faith is ‘the sin that so easily entangles one.’ To maintain a firm faith requires putting up a hard fight for it, resisting men who could plunge one into immorality, combating the works of the flesh, avoiding the snare of materialism, shunning faith-destroying philosophies and traditions of men, and, above all, looking “intently at the Chief Agent and Perfecter of our faith, Jesus.”—Heb 12:1, 2; Jude 3, 4; Ga 5:19-21; 1Ti 6:9, 10; Col 2:8.
Still trying to deny the undeniable.
New Precambrian Embryos Are Equivocal at Best
Evolution News & Views
Precambrian embryos? Old news. Paleontologists have been looking at them for over a decade, yet the Cambrian explosion remains one of the strongest empirical challenges against Darwin's theory. A new paper tries to show that some of them were "possibly" embryos of metazoan animals that emerged long before the explosion, thereby lengthening the time during which evolution could have worked its magic.
In Darwin's Doubt, Stephen Meyer pointed to the embryos as evidence against the "artifact hypothesis." This hypothesis tried to explain the lack of Precambrian ancestors as an artifact of poor fossil preservation. "If these strata could preserve embryos," Meyer said, "then they should have preserved fully developed animals -- at least, if such animals were present at the time" (p. 68). Illustra Media's film Darwin's Dilemma includes Paul Chien, who worked with Dr. J.Y. Chen at the discovery site in China, dissecting some of the fossils, showing them under the microscope to be characteristic of sponge embryos.
The embryos come from the Precambrian Doushantuo formation in China, dated at 600 million years old -- about 60 million years before the onset of the Cambrian Explosion. This was the Ediacaran period, populated by strange-looking sessile colonies of unknown organisms. Meyer discusses the Ediacaran in detail in his book, documenting that most leading evolutionary paleontologists consider the Ediacaran creatures to be unrelated to the Cambrian animals. Meyer readily acknowledges the presence of sponges and possibly two other phyla before the explosion. The problem for evolutionists is to explain the geologically sudden appearance of almost twenty new phyla with new body plans more complex than sponges or anything else that came before - animals with jointed legs, guts, eyes, hard parts, and locomotion. Some of the phyla, like trilobites and Marrella, exhibit bilateral symmetry. These were the first bilaterians: a group that includes us.
Darwin himself confessed that "if numerous species, belonging to the same genera or families, have really started into life all at once, the fact would be fatal to the theory of descent with slow modification through natural selection" (quoted in Meyer, p. 17). His disciples ever since have scoured the earth for evidence of the missing Cambrian ancestors in the strata below. All they have found are microbes, sponges, the Ediacaran biota, and the embryos. A few small shelly fossils appear at the base of the Cambrian (see Debating Darwin's Doubt, Chapters 13-14, for details), but experts consider the Precambrian evidence to be insufficient to account for the profusion of new body plans in the Cambrian explosion.
To muffle the explosion, evolutionists have used two strategies to construct a "long fuse" of gradual evolutionary experimentation. One has been the molecular clock. Molecular estimates of mutation rates, they say, show that the ancestors must have existed, even without fossil evidence. The argument is circular; it relies on evolution to try to prove evolution. Even so, last October, we discussed a Current Biology paper by Telford, Donoghue, and Yang who showed after a detailed analysis that molecular clock data is too imprecise to draw any conclusions.
The other strategy has been to conjure complex animals out of the Precambrian fossil record. In Darwin's Doubt, pp. 90-92, Meyer showed how David Bottjer of the University of Southern California was roundly criticized by his colleagues in 2005 for making too much of an enigmatic fossil named Vernanimalcula. Bottjer had labeled it an early bilaterian, but most others considered it to be irrelevant to the Cambrian explosion (see Casey Luskin's article from 2012 that says Vernanimalcula is possibly not even a fossil at all). Last year we showed Bottjer still suggesting Vernanimalcula was a bilaterian.
Now, in a paper in Geology co-authored by three colleagues from China and an imaging expert in France, Bottjer has more show and tell from Doushantuo. Strangely, he omits mention of Vernanimalcula, noting that for the alleged Precambrian bilaterians, "most of them are not yet widely accepted." (The reference for that comment is to a paper with a very harsh title, "A merciful death for the 'earliest bilaterian,' Vernanimalcula." Clearly the authors, Bengtson, Cunningham, Yin, and Donoghue, disagreed that it was ever "widely accepted.")
The Geology paper presents three new embryos that the authors claim show a cleavage pattern characteristic of metazoan animals, perhaps even bilaterians. Phys.org shares the gist of the new claim:
In their article for Geology, Zongjun Yin and colleagues report new Doushantuo embryo-like fossils. They used high-resolution synchrotron radiation X-ray microtomography to reconstruct three-dimensional structures of the fossils, and the results demonstrate that these fossils preserve unique features directly comparable to living animal embryos that utilize a special kind of cell division pattern known as discoidal cleavage. Given that discoidal cleavage only occurs in animal embryos, the biological affinities of these fossils are probably animals. [Emphasis added.]
Since these embryos are in the Doushantuo formation (dated 600 million years old), there must have been animals alive back then, if not earlier. Problem solved? Well, look at the images and think about the interpretation. First some terminology. In their pre-gastrula stages, embryos show either holoblastic cleavage (where the first cells all look the same size) or meroblastic cleavage (where one cell becomes a large "yolk" for the others). Discoidal cleavage is a type of meroblastic cleavage where the cells sit on top of the yolk cell without penetrating it. Identifying the type of cleavage in these phophatized embryos is the key to interpreting them, they say:
Recently, the debate on the EDEFs [Ediacaran Doushantuo Embryo-like Fossils] has begun to crystallize into two competing interpretations: (1) that the EDEFs represent crown metazoans, or (2) that they represent stem metazoans or nonmetazoan holozoans. These two competing interpretations have very different implications for the timing and tempo of animal diversification [i.e., the Cambrian explosion]. If the EDEFs are crown metazoans, a deep Precambrian history of animals is implied, whereas if they are stem or non-metazoans, the fossils do not reduce the gap between molecular clock estimates and the fossil evidence for the early divergence of metazoans. It is difficult to reconcile these competing interpretations because these morphologically simple EDEFs yield very little phylogenetic information.
And so the authors argue that the appearance of discoidal cleavage suggests that the embryos could be crown metazoans, implying "a deep Precambrian history of animals." Here are some issues:
Only one of the 3 microfossils shows "possible" discoidal cleavage; the others are ambiguous, judging from the images; they only show some cells smaller than one larger cell.
The prime example has 12 smaller cells appearing in an indentation in the large cell. They cannot rule out, however, "taphonomic bias" (artifacts from fossilization) or unequal cleavage in a holoblastic embryo.
Cleavage patterns vary widely among multicellular organisms. While no instances of discoidal cleavage have been "reported" outside of bilaterians, they are not necessarily diagnostic of bilaterians.
Many bilaterians undergo holoblastic cleavage: annelids, mollusks, echinoderms, tunicates, amphibians, some fish, and placental mammals. Some of these are Cambrian phyla; others are advanced vertebrates.
Holoblastic cleavage organisms can be organized into 5 kinds within two categories (see Wikipedia); in other words, there are variations that might be interpreted as meroblastic or discoidal in fossil conditions.
Discoidal cleavage is not universal among bilaterians; it appears in widely separated groups including some fish, sharks, birds, reptiles and monotremes (like platypus).
Fossil embryos represent only a snapshot in time of cells turned to stone. The scientists cannot watch the developmental process unfold.
The authors are hanging an awful lot of interpretation, therefore, on one 250-micrometer fossil that they acid-washed and scanned with radiation, then processed for visualization in software. If this little piece of rock is so important, why are there not hundreds of them in all stages of development? Most importantly, where are the adults? Clearly, the Doushantuo formation was capable of fossilizing higher life stages in great detail. Their absence seems better evidence than the presence of a questionable embryo that, until proven otherwise, could be another sponge. Notice the subjective interpretation in the paper, amounting to little more than possibility thinking:
Our findings support the conclusion that at least some EDEFs possibly represent crown-animals, although their phylogenetic affinity cannot be established because discoidal-type meroblastic cleavage has evolved independently in a variety of animal groups, e.g., scorpions and cephalopods as well as many vertebrates, including some fishes and amniotes.
What is it, therefore, about discoidal cleavage that is worth getting excited about? Keep in mind that Bottjer has demonstrated a strong antipathy to intelligent design, dismissing Darwin's Dilemma as "a creationist movie" in spite of its fully scientific arguments; he took part in the effort to block its showing at the California Science Center; and he promoted Vernanimalcula beyond the evidence enough to rouse the censure of his colleagues.
These points aside, what's convincing is the positive evidence for design in animal development, complex body plans and a biosphere that interacts at all levels on a privileged planet in a finely tuned universe. That's huge. That's Undeniable.
Evolution News & Views
Precambrian embryos? Old news. Paleontologists have been looking at them for over a decade, yet the Cambrian explosion remains one of the strongest empirical challenges against Darwin's theory. A new paper tries to show that some of them were "possibly" embryos of metazoan animals that emerged long before the explosion, thereby lengthening the time during which evolution could have worked its magic.
In Darwin's Doubt, Stephen Meyer pointed to the embryos as evidence against the "artifact hypothesis." This hypothesis tried to explain the lack of Precambrian ancestors as an artifact of poor fossil preservation. "If these strata could preserve embryos," Meyer said, "then they should have preserved fully developed animals -- at least, if such animals were present at the time" (p. 68). Illustra Media's film Darwin's Dilemma includes Paul Chien, who worked with Dr. J.Y. Chen at the discovery site in China, dissecting some of the fossils, showing them under the microscope to be characteristic of sponge embryos.
The embryos come from the Precambrian Doushantuo formation in China, dated at 600 million years old -- about 60 million years before the onset of the Cambrian Explosion. This was the Ediacaran period, populated by strange-looking sessile colonies of unknown organisms. Meyer discusses the Ediacaran in detail in his book, documenting that most leading evolutionary paleontologists consider the Ediacaran creatures to be unrelated to the Cambrian animals. Meyer readily acknowledges the presence of sponges and possibly two other phyla before the explosion. The problem for evolutionists is to explain the geologically sudden appearance of almost twenty new phyla with new body plans more complex than sponges or anything else that came before - animals with jointed legs, guts, eyes, hard parts, and locomotion. Some of the phyla, like trilobites and Marrella, exhibit bilateral symmetry. These were the first bilaterians: a group that includes us.
Darwin himself confessed that "if numerous species, belonging to the same genera or families, have really started into life all at once, the fact would be fatal to the theory of descent with slow modification through natural selection" (quoted in Meyer, p. 17). His disciples ever since have scoured the earth for evidence of the missing Cambrian ancestors in the strata below. All they have found are microbes, sponges, the Ediacaran biota, and the embryos. A few small shelly fossils appear at the base of the Cambrian (see Debating Darwin's Doubt, Chapters 13-14, for details), but experts consider the Precambrian evidence to be insufficient to account for the profusion of new body plans in the Cambrian explosion.
To muffle the explosion, evolutionists have used two strategies to construct a "long fuse" of gradual evolutionary experimentation. One has been the molecular clock. Molecular estimates of mutation rates, they say, show that the ancestors must have existed, even without fossil evidence. The argument is circular; it relies on evolution to try to prove evolution. Even so, last October, we discussed a Current Biology paper by Telford, Donoghue, and Yang who showed after a detailed analysis that molecular clock data is too imprecise to draw any conclusions.
The other strategy has been to conjure complex animals out of the Precambrian fossil record. In Darwin's Doubt, pp. 90-92, Meyer showed how David Bottjer of the University of Southern California was roundly criticized by his colleagues in 2005 for making too much of an enigmatic fossil named Vernanimalcula. Bottjer had labeled it an early bilaterian, but most others considered it to be irrelevant to the Cambrian explosion (see Casey Luskin's article from 2012 that says Vernanimalcula is possibly not even a fossil at all). Last year we showed Bottjer still suggesting Vernanimalcula was a bilaterian.
Now, in a paper in Geology co-authored by three colleagues from China and an imaging expert in France, Bottjer has more show and tell from Doushantuo. Strangely, he omits mention of Vernanimalcula, noting that for the alleged Precambrian bilaterians, "most of them are not yet widely accepted." (The reference for that comment is to a paper with a very harsh title, "A merciful death for the 'earliest bilaterian,' Vernanimalcula." Clearly the authors, Bengtson, Cunningham, Yin, and Donoghue, disagreed that it was ever "widely accepted.")
The Geology paper presents three new embryos that the authors claim show a cleavage pattern characteristic of metazoan animals, perhaps even bilaterians. Phys.org shares the gist of the new claim:
In their article for Geology, Zongjun Yin and colleagues report new Doushantuo embryo-like fossils. They used high-resolution synchrotron radiation X-ray microtomography to reconstruct three-dimensional structures of the fossils, and the results demonstrate that these fossils preserve unique features directly comparable to living animal embryos that utilize a special kind of cell division pattern known as discoidal cleavage. Given that discoidal cleavage only occurs in animal embryos, the biological affinities of these fossils are probably animals. [Emphasis added.]
Since these embryos are in the Doushantuo formation (dated 600 million years old), there must have been animals alive back then, if not earlier. Problem solved? Well, look at the images and think about the interpretation. First some terminology. In their pre-gastrula stages, embryos show either holoblastic cleavage (where the first cells all look the same size) or meroblastic cleavage (where one cell becomes a large "yolk" for the others). Discoidal cleavage is a type of meroblastic cleavage where the cells sit on top of the yolk cell without penetrating it. Identifying the type of cleavage in these phophatized embryos is the key to interpreting them, they say:
Recently, the debate on the EDEFs [Ediacaran Doushantuo Embryo-like Fossils] has begun to crystallize into two competing interpretations: (1) that the EDEFs represent crown metazoans, or (2) that they represent stem metazoans or nonmetazoan holozoans. These two competing interpretations have very different implications for the timing and tempo of animal diversification [i.e., the Cambrian explosion]. If the EDEFs are crown metazoans, a deep Precambrian history of animals is implied, whereas if they are stem or non-metazoans, the fossils do not reduce the gap between molecular clock estimates and the fossil evidence for the early divergence of metazoans. It is difficult to reconcile these competing interpretations because these morphologically simple EDEFs yield very little phylogenetic information.
And so the authors argue that the appearance of discoidal cleavage suggests that the embryos could be crown metazoans, implying "a deep Precambrian history of animals." Here are some issues:
Only one of the 3 microfossils shows "possible" discoidal cleavage; the others are ambiguous, judging from the images; they only show some cells smaller than one larger cell.
The prime example has 12 smaller cells appearing in an indentation in the large cell. They cannot rule out, however, "taphonomic bias" (artifacts from fossilization) or unequal cleavage in a holoblastic embryo.
Cleavage patterns vary widely among multicellular organisms. While no instances of discoidal cleavage have been "reported" outside of bilaterians, they are not necessarily diagnostic of bilaterians.
Many bilaterians undergo holoblastic cleavage: annelids, mollusks, echinoderms, tunicates, amphibians, some fish, and placental mammals. Some of these are Cambrian phyla; others are advanced vertebrates.
Holoblastic cleavage organisms can be organized into 5 kinds within two categories (see Wikipedia); in other words, there are variations that might be interpreted as meroblastic or discoidal in fossil conditions.
Discoidal cleavage is not universal among bilaterians; it appears in widely separated groups including some fish, sharks, birds, reptiles and monotremes (like platypus).
Fossil embryos represent only a snapshot in time of cells turned to stone. The scientists cannot watch the developmental process unfold.
The authors are hanging an awful lot of interpretation, therefore, on one 250-micrometer fossil that they acid-washed and scanned with radiation, then processed for visualization in software. If this little piece of rock is so important, why are there not hundreds of them in all stages of development? Most importantly, where are the adults? Clearly, the Doushantuo formation was capable of fossilizing higher life stages in great detail. Their absence seems better evidence than the presence of a questionable embryo that, until proven otherwise, could be another sponge. Notice the subjective interpretation in the paper, amounting to little more than possibility thinking:
Our findings support the conclusion that at least some EDEFs possibly represent crown-animals, although their phylogenetic affinity cannot be established because discoidal-type meroblastic cleavage has evolved independently in a variety of animal groups, e.g., scorpions and cephalopods as well as many vertebrates, including some fishes and amniotes.
What is it, therefore, about discoidal cleavage that is worth getting excited about? Keep in mind that Bottjer has demonstrated a strong antipathy to intelligent design, dismissing Darwin's Dilemma as "a creationist movie" in spite of its fully scientific arguments; he took part in the effort to block its showing at the California Science Center; and he promoted Vernanimalcula beyond the evidence enough to rouse the censure of his colleagues.
These points aside, what's convincing is the positive evidence for design in animal development, complex body plans and a biosphere that interacts at all levels on a privileged planet in a finely tuned universe. That's huge. That's Undeniable.
When religious extremists collide.
Students, Scientism, and Straw Men
Sarah Chaffee
At the NPR website, Barbara King, an anthropologist at the College of William and Mary, recently addressed Ken Ham's Ark Encounter, stating that we could use more "explicit pushback to anti-science creationist discourse" ("There's No Controversy: Let's Stop Failing Our Children on Evolution"). She recommends that readers speak to local school boards and media, educate their children on evolution at home, and ask politicians about their views on origins. Deluged with comments and emails, King sought to address readers' concerns in a follow-up article ("When Science Stands Up To Creationism").
Unfortunately, she frames skepticism on evolution in the familiar but mistaken terms of religion vs. science. Her narrow critique focuses on things like whether dinosaurs and humans coexisted -- "'walked hand-in-hand' a few thousand years ago" -- rather than grappling with peer-reviewed research that questions neo-Darwinism.
King eschews the term "scientism" -- but does she advocate for it? Describing comments she received on her first article, she notes there was "genuine concern that evolutionary scientists, including me, advocate forcing children to learn one way and one way only." Her response does not alleviate that concern.
She does not bother to rebut intelligent design. After quoting responses that talk about the freedom to believe and about learning all of the evidence, she notes, "So in response to these remarks and others like them, let me say it loud and clear: Freedom to believe anything one wants in the religious sphere is incredibly important." But she goes on to state: "Science isn't about belief." King buys into the simplistic equation of science, whatever it may say at the moment, with "truth." She accordingly dismisses the scientific controversy over neo-Darwinism.
Her description of how science works fits the current state of the evolution debate quite well. She notes, "[Science is] about testing hypotheses, and always seeking out both alternative explanations and data-driven corrections to previous conclusions." King quotes one of the comments left on her article:
Science is the process of learning what is where in the world of knowledge; and we are constantly developing better tools to make better measurements. We are constantly re-drawing the stuff that we suspect might be out there, slowly getting closer and closer to getting the stuff beyond the boundaries of knowledge successfully mapped out, and firmly within the boundaries of what we know. This means there will be a new frontier, and new questions, and maybe some corrections along the way.
If King really believes science is about continuous corrections and questions, she should be friendlier to teaching the scientific controversy over evolution, which attempts to do just that. A growing number of scientists hold that natural selection acting on random mutations cannot fully account for the diversity of life.
In The Edge of Evolution, biochemist Michael Behe examines mutations necessary to develop chloroquine resistance by malaria parasites, and concludes that two simultaneous mutations is the most evolution can accomplish. Furthermore, based on population sizes and frequency of mutations arising, he says, "No mutation that is of the same complexity as chloroquine resistance in malaria arose by Darwinian evolution in the line leading to humans in the past ten million years."
Engaging with the evidence is important -- and so is freedom to discuss dissenting ideas.
King quotes a response from John Ellis, writing at PJ Media, who suggested that her reasoning points to the worldview of scientism. But she opts not to quote the end of his response, which makes clear that objecting to scientism isn't tied to any particular religious belief. A couple of sentences she left out are quite insightful:
You don't need to believe that the earth is only six thousand years old and that dinosaurs walked the earth at the same time as humans in order to see the danger in surrendering the control over education to Barbara King. Regardless of what you think about Ken Ham and Answers in Genesis, it's important to guard the freedom of ideas for all.
Gee, I wonder what Professor King would say in response to a book like Axe's Undeniable, which explores many of the serious, scientific objections to Darwinian evolution. We'll probably never know. Dodging the evidence seems to suit her much better.
Darwinism Vs. the real world XXXIII
When You Don't Have Time to Think: Reflexes
Howard Glicksman
Editor's note: Physicians have a special place among the thinkers who have elaborated the argument for intelligent design. Perhaps that's because, more than evolutionary biologists, they are familiar with the challenges of maintaining a functioning complex system, the human body. With that in mind, Evolution News is delighted to offer this series, "The Designed Body." For the complete series, see here. Dr. Glicksman practices palliative medicine for a hospice organization.
It is our muscles, controlled by our nerves, that allow us to breathe, swallow, move around, and handle things. The peripheral nerves send sensory information about what is going on outside and inside the body to the spinal cord and the brain and from them send back instructions to the muscles to tell them what to do. In my last few articles, I described the sensory receptors, which act as transducers, converting phenomena into information the body can use to survive.
The vestibular apparatus, which detects body motion, and the cochlea, which detects sound, are housed within the inner ear. Light is detected by the retina at the back of the eye. Pressure, light touch, motion, vibration, hot and cold, and pain are detected by sensory receptors in the skin that tell the body what's going on around it. Other receptors keep tabs on what's going on within many of the body's organs.
To control the musculoskeletal system, so it can do what it needs to do, the body uses the proprioceptors located in the joints, tendons, and muscles. In general, purposeful movements are done voluntarily. But to maintain its position or avoid serious injury, sometimes the body must act quickly so that these reflexive movements are done unconsciously. Let's look at how some of these automatic reflexes work to prevent organ damage and help maintain the body's position so that goal directed activities can be done. Keep in mind that when evolutionary biologists tell us about how life arose, they only deal with how it looks and not how it must actually work within the laws of nature to survive. Ask yourself which is a more plausible explanation for how life arose: chance and the laws of nature alone or intelligent design?
A reflex is an involuntary, pre-programmed, automatic motor response to a stimulus that comes about without conscious direction from the brain. It works through the spinal cord and brainstem and serves to protect the body from injury and to maintain its position while the mind is focused elsewhere. For example, the slightest touch of the cornea in the eye triggers blinking immediately. Shining a bright light into the eyes instantaneously makes the pupils close. Without these automatic and quick reflexes, our eyes would be at high risk for injury because the time it would take for our brain to assess the situation and implement a plan to avoid injury would not be fast enough to prevent serious damage.
The simplest reflex, involving just one sensory nerve sending a message to just one motor nerve, is the stretch reflex. The patellar reflex, where tapping on the tendon of a bent knee suddenly straightens it out is the classic example. Tapping the patellar tendon stretches the muscle spindles in the quadriceps muscle, sending nerve impulses through the sensory nerve to the spinal cord. If the impulses are strong enough to stimulate the motor nerve, it instructs the quadriceps to contract, causing the knee to go into extension.
The stretch reflexes are important for maintaining posture and position. Standing with the knees extended for some time eventually results in fatigue of the quadriceps and puts the body at risk of falling. The resulting stretch of the muscle spindles activates the patellar reflex and stimulates the quadriceps to contract more, which stabilizes the knee and prevents a fall. This recovery of posture function takes place throughout the body because the stretch reflex operates in all of the muscles, whether in the head and neck, the arms and legs, or the spinal column.
However the ability for the stretch reflex to maintain the body's position wouldn't be possible without reflex inhibition. The movement of a bone across a joint in any direction usually depends on two complementary muscles working in opposite directions. The quadriceps extends the knee and the biceps femoris flexes it. The patellar reflex not only causes the quadriceps to contract but simultaneously sends nerve messages to relax the biceps femoris. Without reflex inhibition the complementary muscles would constantly be fighting a tug of war with each other and coordinated muscle function would be impossible.
Another important but more complex pattern used by the body to protect itself from injury while maintaining its position is the withdrawal (flexor) and crossed extensor reflexes. If you step on something hot or sharp, the pain messages quickly go to the spinal cord where it stimulates a series of flexor muscles to contract so that you immediately withdraw your foot. But when you lift your leg off the ground, you are at risk of falling. So a split second later, the crossed extensor reflex straightens out your other leg and your body weight shifts over it to maintain your balance. You barely think about any of this -- your body knows to do it naturally.
When it comes to life, real numbers have real consequences. When you stand up your buttocks is about one meter off the ground. If your quadriceps weaken or you suddenly lift your leg off the ground to avoid pain, gravity immediately kicks in. Since gravity makes all things accelerate to the ground at 10 m/sec2, it is possible to calculate how long it would take for you to hit it from one meter up (0.45 sec). This means that your nervous system would have to be able to react fast enough to prevent a fall -- less than half a second.
The impulse velocity of a nerve is faster if it is larger in diameter and insulated with a fatty substance called myelin, rather than smaller and unmyelinated. Normally, the sensory and motor nerves involved in the abovementioned reflexes are large and myelinated and have an impulse velocity of about 100 m/sec (> 200 mph). Since it is about one meter from the foreleg to the lower spinal cord, it only takes about 0.02 sec (0.01 + 0.01) for the nerve impulse to travel along the sensory nerve to the spinal cord and back along the motor nerve for these reflexes to work in time to keep you balanced and on your feet. This would give the neuromuscular system plenty of time to make changes to prevent a fall (0.45 sec).
In contrast, the impulse velocity of the smaller and unmyelinated nerves that inform the body about pain is only about one meter/sec. This means that if the sensory and motor nerves involved in these reflexes were like the pain nerve fibers, it would take at least two seconds for the impulses to go from the leg to the spinal cord and back again. Clearly, this would not be fast enough to prevent you from falling (0.45 sec). This also explains why, when you are injured you can react very quickly to avoid further tissue damage but you don't experience the severe pain until a few seconds later.
The system of reflexes the body uses to protect itself from injury and maintain its position is irreducibly complex because of the different nerve and muscle cells it needs to work. But it also demonstrates natural survival capacity in that the impulse velocity of the sensory and motor nerves involved in these reflexes is sufficient to contend with the force of gravity. Without this, no matter how sophisticated their reflexes, it would have been impossible for our earliest ancestors to maintain their position and survive.
Evolutionary biologists imagine how these systems came into being by how they look, but they rarely seem to think that it's also important to explain how they happen to work within the laws of nature. Next time we'll look at what it takes for the body to keep its balance.
Howard Glicksman
Editor's note: Physicians have a special place among the thinkers who have elaborated the argument for intelligent design. Perhaps that's because, more than evolutionary biologists, they are familiar with the challenges of maintaining a functioning complex system, the human body. With that in mind, Evolution News is delighted to offer this series, "The Designed Body." For the complete series, see here. Dr. Glicksman practices palliative medicine for a hospice organization.
It is our muscles, controlled by our nerves, that allow us to breathe, swallow, move around, and handle things. The peripheral nerves send sensory information about what is going on outside and inside the body to the spinal cord and the brain and from them send back instructions to the muscles to tell them what to do. In my last few articles, I described the sensory receptors, which act as transducers, converting phenomena into information the body can use to survive.
The vestibular apparatus, which detects body motion, and the cochlea, which detects sound, are housed within the inner ear. Light is detected by the retina at the back of the eye. Pressure, light touch, motion, vibration, hot and cold, and pain are detected by sensory receptors in the skin that tell the body what's going on around it. Other receptors keep tabs on what's going on within many of the body's organs.
To control the musculoskeletal system, so it can do what it needs to do, the body uses the proprioceptors located in the joints, tendons, and muscles. In general, purposeful movements are done voluntarily. But to maintain its position or avoid serious injury, sometimes the body must act quickly so that these reflexive movements are done unconsciously. Let's look at how some of these automatic reflexes work to prevent organ damage and help maintain the body's position so that goal directed activities can be done. Keep in mind that when evolutionary biologists tell us about how life arose, they only deal with how it looks and not how it must actually work within the laws of nature to survive. Ask yourself which is a more plausible explanation for how life arose: chance and the laws of nature alone or intelligent design?
A reflex is an involuntary, pre-programmed, automatic motor response to a stimulus that comes about without conscious direction from the brain. It works through the spinal cord and brainstem and serves to protect the body from injury and to maintain its position while the mind is focused elsewhere. For example, the slightest touch of the cornea in the eye triggers blinking immediately. Shining a bright light into the eyes instantaneously makes the pupils close. Without these automatic and quick reflexes, our eyes would be at high risk for injury because the time it would take for our brain to assess the situation and implement a plan to avoid injury would not be fast enough to prevent serious damage.
The simplest reflex, involving just one sensory nerve sending a message to just one motor nerve, is the stretch reflex. The patellar reflex, where tapping on the tendon of a bent knee suddenly straightens it out is the classic example. Tapping the patellar tendon stretches the muscle spindles in the quadriceps muscle, sending nerve impulses through the sensory nerve to the spinal cord. If the impulses are strong enough to stimulate the motor nerve, it instructs the quadriceps to contract, causing the knee to go into extension.
The stretch reflexes are important for maintaining posture and position. Standing with the knees extended for some time eventually results in fatigue of the quadriceps and puts the body at risk of falling. The resulting stretch of the muscle spindles activates the patellar reflex and stimulates the quadriceps to contract more, which stabilizes the knee and prevents a fall. This recovery of posture function takes place throughout the body because the stretch reflex operates in all of the muscles, whether in the head and neck, the arms and legs, or the spinal column.
However the ability for the stretch reflex to maintain the body's position wouldn't be possible without reflex inhibition. The movement of a bone across a joint in any direction usually depends on two complementary muscles working in opposite directions. The quadriceps extends the knee and the biceps femoris flexes it. The patellar reflex not only causes the quadriceps to contract but simultaneously sends nerve messages to relax the biceps femoris. Without reflex inhibition the complementary muscles would constantly be fighting a tug of war with each other and coordinated muscle function would be impossible.
Another important but more complex pattern used by the body to protect itself from injury while maintaining its position is the withdrawal (flexor) and crossed extensor reflexes. If you step on something hot or sharp, the pain messages quickly go to the spinal cord where it stimulates a series of flexor muscles to contract so that you immediately withdraw your foot. But when you lift your leg off the ground, you are at risk of falling. So a split second later, the crossed extensor reflex straightens out your other leg and your body weight shifts over it to maintain your balance. You barely think about any of this -- your body knows to do it naturally.
When it comes to life, real numbers have real consequences. When you stand up your buttocks is about one meter off the ground. If your quadriceps weaken or you suddenly lift your leg off the ground to avoid pain, gravity immediately kicks in. Since gravity makes all things accelerate to the ground at 10 m/sec2, it is possible to calculate how long it would take for you to hit it from one meter up (0.45 sec). This means that your nervous system would have to be able to react fast enough to prevent a fall -- less than half a second.
The impulse velocity of a nerve is faster if it is larger in diameter and insulated with a fatty substance called myelin, rather than smaller and unmyelinated. Normally, the sensory and motor nerves involved in the abovementioned reflexes are large and myelinated and have an impulse velocity of about 100 m/sec (> 200 mph). Since it is about one meter from the foreleg to the lower spinal cord, it only takes about 0.02 sec (0.01 + 0.01) for the nerve impulse to travel along the sensory nerve to the spinal cord and back along the motor nerve for these reflexes to work in time to keep you balanced and on your feet. This would give the neuromuscular system plenty of time to make changes to prevent a fall (0.45 sec).
In contrast, the impulse velocity of the smaller and unmyelinated nerves that inform the body about pain is only about one meter/sec. This means that if the sensory and motor nerves involved in these reflexes were like the pain nerve fibers, it would take at least two seconds for the impulses to go from the leg to the spinal cord and back again. Clearly, this would not be fast enough to prevent you from falling (0.45 sec). This also explains why, when you are injured you can react very quickly to avoid further tissue damage but you don't experience the severe pain until a few seconds later.
The system of reflexes the body uses to protect itself from injury and maintain its position is irreducibly complex because of the different nerve and muscle cells it needs to work. But it also demonstrates natural survival capacity in that the impulse velocity of the sensory and motor nerves involved in these reflexes is sufficient to contend with the force of gravity. Without this, no matter how sophisticated their reflexes, it would have been impossible for our earliest ancestors to maintain their position and survive.
Evolutionary biologists imagine how these systems came into being by how they look, but they rarely seem to think that it's also important to explain how they happen to work within the laws of nature. Next time we'll look at what it takes for the body to keep its balance.
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