In aus.religion.christian John wrote:

It was recently reported in the press that the ‘scientific community’ (for want of better categorization) believes that homo-sapiens and chimpanzees have a common ancestor. They share 99% or thereabouts of the same genes apparently. recently? You mean, in the last 100 years or so?

Chris responded:

Peter is referring to recent genetic studies; and in particular a recent publication in PNAS (May 23, 2003). This publication has received a fair amount of publicity in the popular press.

This post by me is off-topic; I make no attempt to relate to religion. Readers not interested in biological classification schemes can skip now.

The fact that we have a common ancestor with the chimpanzees has been basic common knowledge for more than 100 years.

Contributions of genetics in recent decades has helped to explore the relationship in more detail. Early application of genetic comparisons, for example, helped to single out chimpanzees as our closest relative. To really appreciate the dramatic significance of this result, however, it can be phrased from the chimpanzee perspective.

Humans turn out to be the closest living relatives of chimpanzees. Chimpanzees are closer, genetically, to humans than they are to any of the other apes (excepting another chimpanzee of course; there are three chimpanzee species described in the literature).

This has caused a bit of a problem in taxonomy, since the traditional taxonomy recognizes humans as primates, but put all the apes (gorilla, chimpanzee and orangutang in particular) into a separate primate category.

Now of course, humans have unique characteristics, and some other characteristics which are not necessarily unique but certainly held within humanity to an exceptionally high degree.

So too, any other organism has its own special characteristics. As humans, our special characteristics have particular importance to us, and this is right and proper.

Within biology, and biological classification, however, there are clear regularities and patterns, which means that classification is not an arbitrary grouping but a reflection of a strict pattern of nesting which is apparent in genes, and in morphology. Basically, biological classification turns out to be have a natural and intrinsic hierarchy, whereas other things (like rocks) do not have one obvious hierarchy.

And it turns out that in standard scientific biological classification techniques, when applied to chimpanzees, should put them into a group with humans and gorillas, distinct from orangutangs, as follows:

/—————– orangutangs (at least two species) / / /————— gorillas (at least two species) –+ / \–+ /– modern humans (one species) \ /-+ \ /—+ \– Neandertals (extinct) \–+ \—– Australopithecines (extinct) \ \ /—– chimpanzee (two species?) \-+ \—– bonobo (one species) (pygmy chimpanzee)

Now of course an evolutionist looks at this classification and sees lines of descent from common ancestors. Put another way, evolution is the theory that makes sense of this otherwise very surprising phenomenon of a strong nested hierarchy which is observed in living things.

But you don’t need to be an evolutionist to appreciate the data. The tree above is quite simply the result of objective classification techniques. It is data; not inference. You obtain this tree by taking as much genetic data as you can (omit the Australopithecines, for whom we have no genetic information) and throw it into a classification program which resolves hierarchies, and the tree I have shown is what comes out. The same tree comes out for a whole range of different genetic markers; protein sequences, gene sequences etc. If you apply the data to individual proteins, you can get occasional anomalies, in which a different tree is returned. There is some random noise with small data sets. But when you apply it to a lot of data, this is the one and only tree returned.

You also get the same tree if you apply metric analysis to morphology; though not quite as unambiguously.

This result has been underlined many times over the last decade. It is not new.

What this means is that traditional biological terms fail to match the data when it comes to apes.

The issue comes up again in the most recent PNAS proceedings. (Proc. National Academy of Sciences). The new PNAS report is yet another study, giving the same results. There is nothing new or surprising in the data they have published, to people familiar with this work over the last ten years or so.

What has excited interest is that the report proposes that humans and chimpanzees should be classified in the same genus. The relevant living species would become…

Proposed formal name Current formal name Popular name ——————– ——————- ———— Homo (Homo) sapiens Homo sapiens human Homo (Pan) troglodytes Pan troglodytes chimpanzee Homo (Pan) paniscus Pan paniscus bonobo

This is not really new data. It is rather a proposal for fixing up biological nomenclature to better fit what is known about the biology of the species involved. And the proposal is not new either.

See the summary on-line at <http://www.pnas.org/misc/highlights.shtml#HL4> (this link has a strictly limited lifetime)

The full paper is at <http://www.pnas.org/cgi/content/abstract/1232172100v1> (this link should work long term)

Citation: “Implications of natural selection in shaping 99.4% nonsynonymous DNA identity between humans and chimpanzees: Enlarging genus Homo” by Derek E. Wildman, Monica Uddin, Guozhen Liu, Lawrence I. Grossman, and Morris Goodman PNAS June 10, 2003, vol 100, num 12, pp 7181-7188 published on-line before print at <http://www.pnas.org/cgi/content/abstract/1232172100v1>

Cheers — Chris