Evolution’s Tall Tale — The Giraffe Neck
The giraffe’s neck has long been a beloved icon of evolutionary theory. According to the story, one of the giraffe’s short-necked ancestors had a slightly longer neck, which helped him reach leaves the other animals on the savannah couldn’t. This gave him a survival advantage he passed on to his offspring. Or maybe the female giraffes really dug his slightly longer neck, giving him a reproductive advantage. Same result. He passed his slightly longer neck on to his offspring. Rinse and repeat a few thousand times, and voila, the lineage ends up with 600-pound, six-foot long giraffe necks.
But the devil is in the details. An article in the journal Nature frankly characterizes the evolution of the giraffe’s cartoonishly long neck as “a puzzle”:
There should be a good reason for the extraordinary length, because it causes hardship. A giraffe’s heart needs to pump blood 2 metres up to the head, which requires a high blood pressure and management to avoid fainting or stroke. “It’s beautifully adapted to this, but it’s a big cost,” says Rob Simmons, a behavioural ecologist at the University of Cape Town in South Africa, who was not involved in the study.
One prevailing theory is that giraffes evolved longer necks to reach higher trees for food. “This is widely believed; it’s really entrenched,” says Simmons…. [But] research has shown that giraffes tend to eat from lower levels, and tall giraffes aren’t more likely to survive drought, when food competition is highest. Another idea is that giraffes evolved longer necks for sexual competition, with male giraffes engaging in violent neck-swinging fights and longer necks attracting mates…. [But] males don’t have longer necks than females.1
Fossil Phantasms
Fossils aren’t much help either. German geneticist Wolf-Ekkehard Lönnig surveyed the literature on fossils and giraffe evolution and reports that there is an abundance of fossils from giraffes and creatures said to be either giraffe ancestors or closely related to those ancestors, but what remains stubbornly absent is a smooth series of transitional fossils from short-necked to long-necked. He writes:
No continuous series of fossil links leads to the Giraffa or Okapia. “The giraffe and the okapi of the Congo rain forest are considered as sister groups, the origins of which are still not known” (Devillers and Chaline 1993, p. 247). Similarly Starck (1995, p. 999) remarks: “The ancestry of Giraffidae is disputed.” Wesson (1991, pp. 238-239) agrees with these statements about giraffe fossils, as follows: “The evolving giraffe line left no middling branches on the way, and there is nothing, living or fossil, between the moderate neck of the okapi and the greatly elongated giraffe. The several varieties of giraffe are all about the same height.”
An okapi, keep in mind, is an extant even-toed ungulate that looks not dramatically different from a large deer. Between it and the giraffe there stretches a great morphological gulf.
There was a much-ballyhooed fossil find reported in 2015 purporting to bridge that great gulf. A Live Science article, “7-Million-Year-Old Fossils Show How the Giraffe Got Its Long Neck,” promised the moon, and the lead researcher, Nikos Solounias, was only slightly more restrained. “We actually have an animal whose neck is intermediate [in length] — it’s a real missing link,” he said. But as the evolutionists behind the study later concede, they don’t even think the creature, Samotherium major, is a direct ancestor of the giraffe.
Stretching the Truth
More fundamentally, as researchers learn more and more about giraffe physiology, it’s increasingly clear that hundreds, maybe even thousands, of genetic changes would be needed to arrive at a functioning giraffe; many of the changes would need to arrive simultaneously for the creature to survive; and such big-jump changes would need to occur numerous times over millions of years.
Yes, natural selection could jump in to preserve these coordinated mutation freak events if they ever occurred, but first the freak-event mutations would have to occur.
Oxford biologist Richard Dawkins, famous for his many books defending atheism and evolutionary theory, characterizes the difference between a giraffe’s neck and that of its short-necked ancestor as relatively “slight.” Dawkins writes: “The giraffe’s neck has the same complicated arrangement of parts as the okapi (and presumably as the giraffe’s own short-necked ancestor). There is the same sequence of seven vertebrae [Lönnig contests this], each with its associated blood vessels, nerves, ligaments, and blocks of muscle. The difference is that each vertebra is a lot longer, and all its associated parts are stretched or spaced out in proportion.”2
So, how hard could it be to evolve?
Dawkins’s characterization is one a Darwin disciple could love, but never an attentive engineer, or any biologist with a working familiarity with giraffe physiology. As Lönnig puts it, Dawkins “simplifies the biological problems to a degree that is tolerable for evolutionary theory, but not realistic with regard to the biological facts.”
Giraffe Spectacular
Lönnig describes several things that must be either engineered or reengineered to arrive at a functional giraffe from a short-necked ancestor. First, giraffes, like cows and many other grazing animals, are ruminants, meaning they regurgitate a half-digested cud and chew on it before swallowing the food a second time, helping them digest tough fibrous grass and leaves. But to pull off this trick, a giraffe, with its neck as tall as a man, needs “a special muscular esophagus,” Lönnig explains. So that’s one reengineering challenge.
Lönnig gives so many more that there isn’t room for them all here. His book debunking giraffe evolution, The Evolution of the Long-Necked Giraffe, is dense and thorough. But he helpfully quotes Gordon Rattray Taylor, who concisely summarized several of the reengineering challenges in his book The Great Evolution Mystery:
Nineteenth-century observers assumed that the giraffe had only to develop a longer neck and legs to be able to reach the leaves which other animals could not. But in fact such growth created severe problems. The giraffe had to pump blood up about eight feet to its head. The solution it reached was to have a heart which beats faster than average and a high blood pressure. When the giraffe puts his head down to drink, he suffers a rush of blood to the head, so a special pressure-reducing mechanism, the rete mirabile, had to be provided to deal with this. However, much more intractable are the problems of breathing through an eight-foot tube. If a man tried to do so, he would die — not from lack of oxygen so much as poisoning by his own carbon dioxide. For the tube would fill with his expired, deoxygenated breath, and he would keep reinhaling it. Furthermore, one study group found that the blood in a giraffe’s legs would be under such pressure that it would force its way out of the capillaries. How was this being prevented? It turned out that the intercellular spaces are filled with fluid, also under pressure — which in turn necessitates the giraffe having a strong, impermeable skin. To all these changes one could add the need for new postural reflexes and for new strategies of escape from predators. It is evident that the giraffe’s long neck necessitated not just one mutation but many — and these perfectly coordinated.3
Percival Davis and Dean Kenyon cogently tease out the significance of all this:
In short, the giraffe represents not a mere collection of individual traits but a package of interrelated adaptations. It is put together according to an overall design that integrates all parts into a single pattern. Where did such an adaptational package come from? According to Darwinian theory, the giraffe evolved to its present form by the accumulation of individual, random changes preserved by natural selection. But it is difficult to explain how a random process could offer to natural selection an integrated package of adaptations, even over time. Random mutations might adequately explain change in a relatively isolated trait, such as color. But major changes, like the macroevolution of the giraffe from some other animal, would require an extensive suite of coordinated adaptations.4
A Lottery-Winning Fiend
This means that if we hold to the evolutionary story for the giraffe neck, we must go from believing that the giraffe lineage won a series of longshot lotteries over millions of years to believing that the various ancestors in the lineage each won numerous longshot lotteries simultaneously and managed to do this over and over.
To grasp the enormous difference, imagine that the President of the United States takes a winding summer trip through the American heartland and buys a state lottery ticket in each of those 45 states that has a state lottery. (Not all do.) Later that summer it emerges that every one of the lottery tickets the President bought was a jackpot winner. The President’s handlers attribute this to “dumb luck,” but you can bet that 45 state lottery commissioners will smell a rat and, if brave enough, launch an investigation. They will reasonably infer that all those wins were somehow gamed in the President’s favor — that is, were intelligently designed. There are long odds, and then there are odds so long, and so beneficial to someone, that reasonable people begin to look for other explanations.
In the giraffe’s case, a bit of reasoning goes a long way. Blind evolution doesn’t look ahead and coordinate a group of changes for some future advantage. It’s blind and must proceed by one small useful step at a time. No evolutionist, for instance, believes that a small number of mega-mutations turned a land mammal into a whale.
But what if loads of changes are needed simultaneously to successfully make a biological transition, or even just a significant step in a larger transition? We know of only type of cause with the demonstrated ability to meet such a challenge, and it isn’t dumb luck and natural selection. The engineering marvel that is the giraffe, long neck and all, was intelligently designed.
No comments:
Post a Comment