Evidence for a relationship between apes and humans

Young earth creationists sometimes say that it is impossible for humans and the great apes to be descended from a common ancestor, because their genes are more different than you would expect, if that were the case.

I recently read a post, by R. Joel Duff, that has been up for a few years, but is still relevant and interesting. It examines the evidence on the point above, based on mitochondrial DNA. All animals have mitochondria, which are necessary for a cell to obtain energy from food molecules. Mitochondria have only a dozen or so genes, so it is much easier to get a DNA sequence from, say, fox mitochondrial DNA, than from the entire fox genome. Also, mitochondria are passed from one generation to another in the egg cell, with no recombination with male-derived DNA, so there is little change from generation to generation,

Duff examined available data on mitochondrial differences between various animals, including humans. His findings included the following:

Humans vs. Chimpanzees: out of 16569/16569 base pairs, 91.2% were the same.
Red Fox vs. Wolf: out of 13785 fox/16054 wolf base pairs, 86% were the same.
Domestic cat vs. leopard: out of 14352 cat/16206 leopard base pairs, 89% were the same.

For further discussion, more comparisons, and indications of methods, see Duff's post.

Young-earth creationists mostly claim that, following the Ark's landing, less than 5,000 years ago, less than 200 kinds (baramins) of animals were released, and these animals rapidly evolved so as to produce several, perhaps even many, species each. These animals, they say, mostly did not look like the animals of today, or the animals shown in story books about creation, or the Ark. For example, there were a pair, or perhaps seven pairs, of ancestors of all dog/wolf/fox-like animals, which evolved into coyotes, wolves, foxes, wild dogs, dingoes, and more types of present animals, and there were ancestors of all catlike organisms, which evolved into lions, tigers, panthers, ocelots, and more creatures. The "more" is said, by most Young-earth creationists, to include extinct creatures, such as saber-tooth tigers. Answers in Genesis, the most prominent Young-earth creationist organization, says this: "In addition to all the big cats that filled the earth after the Flood and then went extinct (such as the saber-toothed cat), forty species of cats survive."

There is, so far as I know, no scientific, or historical, evidence to support such claims, and what evidence exists from ancient art also does not support them. As far as we can tell, lions, and most other animals, have changed little over the past several thousands of years.

Duff's post is one of many that point out scientific evidence against the current Young-earth creationist paradigm.
 
Duff's conclusion is that, although mitochondrial DNA does not tell the whole story, comparing mitochondrial DNA indicates that the claim, that humans and the great apes are too different to be in the same kind/baramin, does not hold up. The proposed canine and feline kinds/baramins have more differences among them than humans and chimpanzees do between them. Duff also, wisely, says this: "I make no claim that the data I present are convincing evidence of common ancestry or of the lack of common ancestry."

Thanks for reading. Read Duff's post -- in fact, if you can, subscribe to his blog.

Did 90% of all animal species arise at the same time as humans?

Recent articles on-line have alleged that about 90% of all animal species came to be at the same time as humans. See this post for references to four such articles.

What is this idea based on? This article is the main reason for such an idea. (The link given is to a summary. The summary includes a link to the full technical article it is based on, which is freely accessible.) A technique known as DNA barcoding was used. DNA barcoding usually compares a small amount, about 600 base pairs, of the mitochondrial DNA of different organisms. Mitochondria have DNA which is separate from the DNA in the cell's nucleus. DNA barcoding has been used, for example, to check the identity of fish sold for food -- are cheaper fish being passed off as more expensive ones? In some cases, the answer has been "yes." Mitochondria are passed on by females, as sperm do not have mitochondria. To quote from the summary of the article: 
Several convergent lines of evidence show that mitochondrial diversity in modern humans follows from sequence uniformity followed by the accumulation of largely neutral diversity during a population expansion that began approximately 100,000 years ago. A straightforward hypothesis is that the extant populations of almost all animal species have arrived at a similar result consequent to a similar process of expansion from mitochondrial uniformity within the last one to several hundred thousand years.

If true, this has important implications for origins. Ken Ham's blog has posted as article about this idea, and, not surprisingly, claims that these findings are consistent with his young-earth creation model, with survival of land animals after the flood, and not consistent with mainstream evolutionary thought. Perhaps so. Ham does note that the time for this increase in diversity suggested, 100,000, or more, years ago is not consistent with his model, which claims that all land animals arose about 6,000 years ago. He says that the difference in time is because of wrong evolutionary assumptions by mainstream biologists.

It seems premature to reach any firm conclusions on this matter. There have been some substantive criticisms of the barcoding method being applied to taxonomy. This article, from an important journal, Systematic Biology, strongly argues that taxonomic conclusions should not be drawn from only one type of data, be that DNA barcoding, the fossil record, or something else. The article isn't against young-earth creationism, in fact doesn't mention it, but it is against not using all types of data in developing taxonomic relationships. "Systematic," in this context, has to do with classifying organisms.

The Systematic Biology article also indicates some possible problems with DNA barcoding, and points out that the original article, quoted above: "... never [claims] that most 'species' came into existence within the past 200,000 years. Rather, what has come into existence within that time frame is the genetic variation observed in one gene in the mitochondrial genome."

DNA barcoding results, although interesting, and sometimes useful, should not be taken as overwhelming scientific proof of young-earth creationism, at least not yet. And, if such proof becomes stronger, the "young" of young-earth creationism may need revision to considerably more than six to ten thousand years ago.

I'm not sure how the remaining 10% of animal species are supposed to have originated, if, indeed, about 90% of them originated close to one time.

Thanks for reading.