بسم الله الرحمن الرحيم، وصلوات الله وسلامه على أشرف المرسلين
In the name of God, Most Gracious, Most Merciful.
Check out part 1 here if you haven’t already, which was an intro to this series of posts. In this article, I’ll dive into the evidence that is brought forward to support human-chimp common ancestry, starting with the alleged similarities that exist between us and them.
Similarity as Evidence of Common Descent
From the Smithsonian website:
Geneticists have come up with a variety of ways of calculating… how similar chimpanzees and humans are. The 1.2% chimp-human distinction, for example, involves a measurement of only substitutions in the base building blocks of those genes that chimpanzees and humans share. A comparison of the entire genome, however, indicates… an additional 4 to 5% distinction between the human and chimpanzee genomes…
Humans, chimpanzees, and bonobos are more closely related to one another than either is to gorillas or any other primate. From the perspective of this powerful test of biological kinship, humans are not only related to the great apes – we are one. The DNA evidence leaves us with one of the greatest surprises in biology: the wall between human, on the one hand, and ape or animal, on the other, has been breached.
So basically: our genes are similar, therefore we’re related, and therefore there’s no difference between humans and animals. The last part of that (“we are one”) is a philosophical and quasi-religious statement, and it’s absurd that a government-run website is allowed to promote such ideas, but that’s a topic for a later day. More relevant to this article, notice how genetic similarity is referred to as a “powerful test of biological kinship.”
The problem is there’s an underlying assumption at work: the idea that similarities between two species must be caused by them having a common ancestor. There are many rational and empirical problems with such an assumption. The first problem is that even Darwinian Evolution advocates admit that “convergent evolution” happens often as part of their theory: different species evolving the same things at different times and places, on a behavioral, anatomic and even genetic level. Without this concept, the Darwinian tree of life would be even more muddled than it already is. What this means is that while similarity might increase the likelihood of common ancestry, it does not by itself prove common ancestry.
One field where similarities are used to prove common descent is etymology. If two languages have a similar word for the same object, we can infer that they may have evolved from the same ancestor language, perhaps through a gradual process. The reason this makes sense is because there are many possible sounds that can be made to describe an object, so the chance of convergent evolution is low. For example, the Urdu-Hindi word sitara means “star” (as in the celestial object), and from this an Indo-European ancestor word can be inferred – despite the absence of direct evidence – because the English and Urdu sound so similar. Urdu could have just as easily used the word “werzgoop” to describe stars, and that would have served the function of describing stars.
Whereas in biology, there are only so many efficient ways to do certain tasks: walk, see, hear, talk, use tools, climb trees, swim, fly, peel bananas, pick apples, etc. And there are only so many DNA sequences that will produce functional proteins or do other things. The “search space” for possible biological forms to accomplish these tasks is very small. So a parallel convergent origin can happen a lot more. This means we’re not justified in always assuming common ancestry based on similarities.
For humans, it should be noted that we’re living in the same environment as other species, eating similar foods, and carrying out similar tasks. It makes sense that we have a lot in common with them, because many of our biological features were created towards those functional ends. You don’t need common ancestry to explain this. Rather, it’s entirely possible that we were created separately, but with similar features.
Takeaway: an unstated assumption in much of evolutionary theory is the idea that similarity between two species means they share a common ancestor. This is true sometimes, but not always.
Common Descent Assumption Leads To Problems
When assumptions such as “similarity = common descent” are treated as hard facts, it leads to contradictions and absurdities in the history of life. Often times you find very similar species coming about in faraway lands. A parallel convergent origin is a better way to explain this, but some insist on applying common descent anyway, which causes problems.
One example of such a problem: you have similar-looking iguanas native to Fiji and Tonga as well as the Americas. If you assume common descent, this means that at some point, iguanas made the journey 6,000 miles across the ocean and landed in the Pacific islands. It’s theorized that they hitched a ride on logs and that iguanas in the past somehow could survive for months without water.
Another example: there are monkeys that are indigenous to both South America and Africa. Assuming they have a common ancestor, that means that at some point, monkeys made the journey from one region to the other. It’s theorized that monkeys built “rafts” and sailed across the Atlantic Ocean. Yes, you read that right. This is not a joke or parody. Serious evolutionary scientists believe, with a straight face, that monkeys built rafts and sailed across the ocean.
A much better solution is to relax the assumptions: maybe similarity doesn’t always imply common descent, even if it increases the likelihood in some circumstances. And all the assumptions should be clearly articulated and stated, not assumed as facts.
Takeaway: if the belief that similarity means common descent is taken as a hard-and-fast rule, it leads to absurdities in the evolutionary history of life. It’s better to relax the assumption.
The above argument (“it makes sense that we have a lot in common with them, because many of our biological features were created towards those functional ends”) applies in cases where that biological feature is useful or necessary for an organism. One example is opposable thumbs, which we use all the time. But where two species share a biological feature that doesn’t have any use, this argument might not apply.
- “Junk” DNA: most of our DNA doesn’t encode proteins, so some people have claimed that it’s junk. We share a lot of this DNA with chimps and other species also.
- Vestigial organs: organs that aren’t used. The classic example of this is the appendix. It’s claimed that since we don’t need it now, an alleged ancestor species of ours may have needed it and we got it as a leftover.
- Pseudogenes: these are genes that produce faulty proteins. We share a lot of pseudogenes with other mammals.
- Synteny: this refers to the arrangement of the genes along the chromosomes, which is also very similar between humans and chimps.
The argument is that because these things don’t really have functions, the only way to explain them is with reference to common descent. This is correct, if you make the following assumptions:
- They don’t actually have a function.
- A function for them won’t be discovered in the future.
- “Function” is limited to that which measurably provides material benefit.
These assumptions are either definitively false or at least doubtful, for all the above examples.
“Junk” DNA has been shown to be a myth. The DNA that doesn’t encode proteins has other extremely important functions, such as gene regulation. And no organ in the human body is truly vestigial; biologists have identified important uses for the appendix.
The tailbone is another commonly-cited example of a “vestigial” organ, and is featured prominently in the liberal media site Vox’s video on “proof” of human evolution, which currently has 28 million views. However, the tailbone has both material functions, in that it helps with mobility, as well as a deeper purpose, in that it is the first part of the body that will be brought back when we are resurrected on the Day of Judgement. So, this is an example of where assumption #3 above doesn’t apply.
As for pseudogenes and synteny: this is somewhat beyond the level of this article, but these things have actually been shown to be functional in various ways. If you’re interested in more information, I can send you articles or references giving the details on research. Or, read Section VIII in Chapter 15 of the Theistic Evolution book which I mentioned in the intro post. Furthermore, this is an area of active research, so it’s likely that even more functions will be discovered in the future.
So overall, the same argument I mentioned above applies. Common descent is one interpretation of this evidence, but it’s also possible that they were created for a specific function. The evidence isn’t conclusive for common descent between humans and apes.
Takeaway: allegedly non-functional similarities are actually functional. They don’t provide incontrovertible evidence that we have common ancestry with apes.
Overstating the Similarities
This is beyond the scope of this article, but check out the book Aping Mankind: Neuromania, Darwinitis and the Misrepresentation of Humanity by Raymond Tallis where he demonstrates how evolutionary scientists exaggerate the similarities between humans and apes, and gloss over the severe differences. This is done with a desire to promote human evolution, and certain social and political theories seen as deriving from it. Here is one quote from the book (source):
The desire to minimize human uniqueness has prompted exaggerated claims about animal tool use, about their range and mode of communication and their sense of each other, about their putative beliefs and other modes of thought. However, the monuments of collective endeavour seen in the animal kingdom – for example the heaps created by termites – are the result not of conscious deliberation but of dovetailing automaticities.