Jerry Coyne, in his book, Why Evolution is True, presents atavisms as an evidence of evolution. What is an atavism? Coyne says, “These sporadically expressed remnants of ancestral features are called atavisms” (1) and goes on to say, “They differ from vestigial traits because they occur only occasionally rather than in every individual.” (1)
Wikipedia adds, “Atavism is the tendency to revert to ancestral type. In biology, an atavism is an evolutionary throwback, such as traits reappearing which had disappeared generations before.” (2) The Merriam-Webster online dictionary defines atavisms as the “recurrence in an organism of a trait or character typical of an ancestral form and usually due to genetic recombination.” (3)
Atavisms are believed to occur because “they come from the reexpression of genes that were functional in ancestors but were silenced by natural selection when they were no longer needed. Yet these dormant genes can sometimes be reawakened when something goes awry in development.”
Below, I’d like to consider some of the more common ‘atavisms.’ While I reject some of these altogether, I don’t have a problem with those that reflect nothing more than a loss of information within a species. I’ll make the distinctions under each heading.
Examples of Atavisms
- “The most famous genuine atavisms are probably the legs of whales. We’ve already learned that some species of whales retain vestigial pelvises and rear leg bones, but about one whale in 500 is actually born with a rear leg that protrudes outside the body wall. These limbs show all degrees of refinement, with many of them clearly containing the major leg bones of terrestrial mammals – the femur, tibia, and fibula. Some even have feet and toes!” –Jerry Coyne (1)
- First of all the so-called ‘pelvic bones’ are not vestigial hind-legs, but serve a known function even today!
- Anchor points for special muscles used in reproduction.
- Different in males & females.
- “Perhaps they serve some function such as helping to support the whales reproductive anatomy.” –Austin Cline (13)
- Jim Dines, the Collections Manager of Mammalogy at the Natural History Museum of L.A. County: “People that really know the reproductive biology of whales and dolphins already know and have known that these pelvic bones are an anchor point for reproductive organs.” (15)
- “That the modern whale’s pelvis is still used for help in reproduction does not change the fact that it is vestigial.” –Evolutionwiki (12)
- The ‘evidence’ of whale legs (with digits) is very anecdotal as evidenced by the talkorigins website.
- “On October 28, 2006, Japanese fishermen captured a four-finned dolphin off the coast of western Japan, and donated the whale to the Taiji Whaling Museum where it is currently being studied. This bottlenose dolphin has an extra set of hindlimbs, two well-formed palm-sized flippers that move and flap like the normal fore-flippers. As with other atavistic structures, these limbs are likely the result of a rare mutation that allows an underlying, yet cryptic developmental pathway to become reactivated.” –Douglas Theobald, Ph.D (5)
- Katsuki Hayashi, director of the Taiji Whaling Museum said that, “Though odd-shaped protrusions have been found near the tails of dolphins and whales captures in the past, researchers thought it was the first time one had been found with well-developed, symmetrical fins.” (8)
- Is this yet another example where the data is interpreted in light of evolutionary presuppositions? Notice how Theobald sees the hindlimbs and concludes they are “likely” due to the reactivation of old genes from its evolutionary past.
- This is clearly a mutation, and perhaps it is nothing more than that. Some humans are born with three nipples, an extra finger or toe (polydactyly). Some cats are born with four ears (6).
- Regarding the accounts of whales with legs, Carl Wieland with Creation Ministries International has noted, “There is a complex DNA program which causes the development of the normal bone in this part of the whale’s anatomy. A mutational defect in this program could easily cause one or more extra pieces of bone to form, which would almost inevitably be in the same region, either separate from or fused with the normal bone. In the same way, people can be born with extra fingers, ribs, nipples, etc. If this should extend to two extra pieces of bone, no matter how misshapen or otherwise these were, enthusiastic evolutionists would no doubt interpret one additional piece of bone as a ‘femur,’ and any second one would be labeled a ‘tibia’ (shin bone).” (7)
- It also seems that much of the ‘whale leg’ evidence is anecdotal. It’s hard to find solid information online (in the form of pictures, findings, etc.). More often than not, this is an assertion made with little evidence to back it up.
- Finally, I will only point out that, regarding whale evolution, it is commonly asserted that the “ancestor” of modern whales, the Basilosaurus, had hind legs. But this claim reflects evolutionary presuppositions yet again:
- From an August 2010 National Geographic article by Tom Mueller: “Basilosaurus was indeed a whale, but one with two delicate hind legs, each the size of a three-year-old girl’s leg, protruding from its flanks. These winsome little limbs—perfectly formed yet useless, at least for walking—are a crucial clue to understanding how modern whales, supremely adapted swimming machines, descended from land mammals that once walked on all fours.” (16)
- And yet consider these two points:
- The same article by Mueller admits that these ‘hind legs’ had a purpose: “Though unable to support a Basilosaurus’s weight on land, these legs weren’t completely vestigial. They had attachments for powerful muscles, as well as functional ankle joints and complex locking mechanisms in the knee. Gingerich speculates that they served as stimulators or guides during copulation.” (16)
- The Basilosaurus is believed by many to have nothing to do with whales. “The serpentine form of the body and the peculiar shape of the cheek teeth make it plain that these archaeocetes could not possibly have been the ancestor of modern whales.” –Barbara Stahl, a vertebrate paleontologist and evolutionist
- It is believed that horses evolved from smaller, five-toed ancestors.
- Toe development in horses:
- Horse embryos begin development with three toes.
- Later, the middle toe begins to grow faster. At birth, the smaller two toes are left as thin “splint bones”
- “On rare occasions, though, the extra digits continue developing until they become true extra toes, complete with hoofs…This is exactly what the ancient horse Merychippus looked like 15 million years ago.” –Jerry Coyne
- Creationists accept a “loss of information.” Even Coyne acknowledges in this case that the ancient three-toed ancestor of modern horses was a horse!
- Jerry Coyne notes, “Rarely…a baby is born with a tail projecting from the base of its spine. The tails vary tremendously: some are ‘soft,’ without bone, while others contain vertebrae – the same vertebrae normally fused together in our tailbone. Some tails are an inch long, others nearly a foot. And they aren’t just simple flaps of skin, but can have hair, muscles, blood vessels, and nerves. Some can even wiggle.” He concludes, “What could this mean, other than that we still carry a developmental program for making tails? Indeed, recent genetic work has shown that we carry exactly the same genes that make tails in animals like mice, but these genes are normally deactivated in human fetuses.” (1)
- In an article by Dr. Fred Ledley called “Evolution and the Human Tail” that appeared in the May 20, 1982 issue of The New England Journal of Medicine, he argued that the rare human tail is proof-positive for evolution. But then, later in the article, he says this: “When the caudal appendage is critically examined, however, it is evident that there are major morphologic differences between the caudal appendage and the tails of other vertebrates. First of all, the caudal appendage does not contain even rudimentary vertebral structures.… Secondly, the appendage is not located at the caudal terminus of the vertebral column. It is possible that this structure is merely a dermal appendage coincidentally located in the caudal region. This possibility cannot be excluded.” (14)
- Gary Parker, a creationist, responds: “The nervous system starts stretched out open on the back. During development, it rises up in ridges and rolls shut. It starts to ‘zipper’ shut in the middle first, then it zippers toward either end. Once in a while it doesn’t go far enough, and that produces a serious defect called spina bifida. Sometimes it rolls a little too far. Then the baby will be born – not with a tail, but with a fatty tumor. It’s just skin and a little fatty tissue, so the doctor can just cut it off.” (4)
- Even if there are rare cases where a baby is born with a tail, it is not much different than cases where babies are born with extra fingers or toes. The genetic information that exists for the vertebra is already there and so bony “tails” would be a mutation of already-existing genetic information. This is a case where evolutionary presuppositions force an unnecessary conclusion from the data.
- Some have argued that humans have pseudogenes that, when reactivated, may be the cause of these atavistic tails:
- According to TalkOrigins: “In fact, the genes that control the development of tails in mice and other vertebrates have been identified (the Wnt-3a and Cdx1 genes)…As predicted by common descent from the atavistic evidence, these tail genes have also been discovered in the human genome.” (18)
- Even though both the Wnt-3a and Cdx1 genes allegedly play a role in tail formation in mice, these genes have other known functions in humans. (18)(19)
Wings in Earwigs
- From the Orkin website: “There are over 1,500 species of earwigs documented, and most species of earwigs have wings. The name of the biological order which they belong, Dermaptera, actually means leather or skin wings. The front wings, or forewings, are not clear but rather are darker and more durable. Even though most species of earwigs have wings, not all species fly.” (11)
Dew Claw in Dogs
- “The dewclaws are not dead appendages. They can be used to lightly grip bones and other items that dogs hold with the paws.” -Wikipedia (9)
- “The dewclaw served as a purpose in ancient dogs, but isn’t not relevant for modern canines. In the wild and today, the extra digit helped canines climbing or holding objects such as the dead animals they were snacking on…” –Jane Meggitt, The Purpose of the Dewclaw on Dogs, “The Daily Puppy” (10)
- So it appears that this is yet another example of a loss of function or and potentially a loss of information. This is acceptable within the creation model.
Other “atavisms” that can be explained as mutations of already-existing genetic information
- Extra toes in guinea pigs and salamanders
- Why aren’t…
- Humans occasionally born with gills or fins?
- Dogs occasionally born with scales?
- In other words, clear examples of structures that do not relate to the organism at all.
- And why don’t we see a gain in new features?
- Many of these ‘atavisms’ reflect a resurgence of an old trait or feature, which only proves a loss of information and/or loss of function. This fits in the creation model. (i.e. dewclaws)
- Many of these ‘atavisms’ involve a mutational duplication of pre-existing genetic information (extra fingers and toes. Creationists do not deny that such occurs. (i.e. human tails, whale legs).
- If evolution is true, there ought to be a much wider and more frequent occurrence of atavisms, such as humans being born with gills, scales or fins.
- Many of these atavisms reflect an evolutionary presupposition.
(1) Jerry Coyne, “Why Evolution is True,” 2009, pg. 64
(8) http://creation.com/a-dolphin-with-legs-not, originally reported on breitbard.com