August 19, 2006

Our closest relative: the orangutan?

It is commonly theorized that the closest relatives of humans are chimpanzees (Pan troglodytes). A new paper by Jeffrey Schwartz proposes that we are rather more closely related to the orangutans (genus Pongo). Schwartz argues that the genetic similarity between humans and chimps is not a reliable guide to their phylogenetic relationships, and humans share many exclusive traits in common with orangutans.

This is certainly a controversial thesis, and I am not holding my breath that the consensus will change any time soon, but we should definitely give it a proper hearing. In the very least, if morphology and genetics don't agree, we should not a priori assign precedence to genetics. Genetics is "harder" evidence for relatedness than morphology; on the other hand, genes can't be studied for fossil hominids dating to millions of years in the past.

Will our real closest relative please stand up?

Mona Lisa Smile: The Morphological Enigma of Human and Great Ape Evolution. The Anatomical Record (Part B: New Anatomist) 289B: 139-157

The science of human evolution is confronted with the popular chimpanzee theory and the earlier but largely ignored orangutan theory. The quality and scope of published documentation and verification of morphological features suggests there is very little in morphology to support a unique common ancestor for humans and chimpanzees. A close relationship between humans and African apes is currently supported by only eight unproblematic characters. The orangutan relationship is supported by about 28 well-supported characters, and it is also corroborated by the presence of orangutan-related features in early hominids. The uniquely shared morphology of humans and orangutans raises doubts about the almost universal belief that DNA sequence similarities necessarily demonstrate a closer evolutionary relationship between humans and chimpanzees. A new evolutionary reconstruction is proposed for the soft tissue anatomy, physiology, and behavioral biology of the first hominids that includes concealed ovulation, male beard and mustache, prolonged mating, extended pair-bonding, “house” construction, mechanical “genius,” and artistic expression.

Link (pdf)

1 comment:

Bob Browne said...

I'm a convert to Orangism!