Continuing with my series on the evolution of humans (in my previous posts, I discussed the split between chimpanzees & bonobos, and humans), today I will look into the possible links between humans and orangutans.
The orangutan
The orangutans are the great apes that live in Asia (the other great apes are African). Their habitat, encroached by humans has reduced their geographic territory that spanned Southeast Asia and the south of China and now is reduced to some areas of Indonesia, in Sumatra and Borneo.
Orangutans (by the way, their name, in Malay, means orang = "man" and hutan = "forest"; "forest person"), belong to the genus Pongo and comprise three separate species, one living in Borneo (P. pygmaeus) and the other two in Sumatra (P. abelii and P. tapanuliensis).
Nevertheless, we share roughly 97% of our genome with the orangutans. They are believed to have split from the rest of the hominids (that include humans and the African great apes) around 9 to 13 million years ago (Source). With such a distant split time, it is difficult to believe that we may descend from them. The orthodox viewpoint is that we split from a common ancestor of the chimpanzee lineage some 6 million years ago.
The first to propose some kind of ancestry between humans and apes was the French naturalist Jean Baptiste Lamarck (1744-1829), in his work Philosophie Zoologique, p.352 he describes the Angola orang (chimpanzee) as "the most highly developed of animals; it is far superior to the orang of the Indies (Simia satyrus L.) —known as the orangutan—yet, in terms of physical structure, both are vastly inferior to man in both bodily and intellectual faculties." So, the chimpanzee was also known as "orang", but clearly the Indonesian ("Indies") variant was the real orangutan.
Charles Lyell (1797-1875) in his Principles of Geology p.575, criticized "Lamarck's theory of the transformation of the orang-outan into the human species" (worth reading). Later, Charles Darwin, applied Lyell's geological ideas to biology and created the theory of evolution by natural selection (published in his famous book, On the origin of species, 1859). Darwin also wrote about the origin of modern humans in his work "The Descent of Man", 1871 see p. 240, where he speculates the birthplace of humans "In each great region of the world the living mammals are closely related to the extinct species of the same region. It is therefore probable that Africa was formerly inhabited by extinct apes closely allied to the gorilla and chimpanzee ; and as these two species are now man’s nearest allies, it is somewhat more probable that our early progenitors lived on the African continent than elsewhere. But it is useless to speculate on this subject; for two or three anthropomorphous apes, one the Dryopithecus of Lartet, nearly as large as a man, and closely allied to Hylobates, existed in Europe during the Miocene age; and since so remote a period the earth has certainly undergone many great revolutions, and there has been ample time for migration on the largest scale" This is often cited by Out-Of-Africa supporters who only mention the first part (African origin from chimps or gorillas), omitting the second part (possible Eurasian origin and migration). He adds, on p. 255 "We may thus ascend to the Lemuridae; and the interval is not very wide from these to the Simiadae. The Simiadae then branched off into two great stems, the New World and Old World monkeys; and from the latter, at a remote period, Man, the wonder and glory of the Universe, proceeded." Indeed, we split from Old World apes, but which? Chimpanzees or orangutans?
We share many traits with Orangutans
There are many similarities that reveal that we are closer to them than to chimpanzees. For instance: roughly 0.8% of our genome is closer to orangutans than to chimpanzee. See: Hobolth, A. et al. Incomplete lineage sorting patterns among human, chimpanzee, and orangutan suggest recent orangutan speciation and widespread selection. Genome Research 21, 349-356 (2011); and Locke, D.P. et al. Comparative and demographic analysis of orangutan genomes. Nature 469, 529-533 (2011).
John Grehan of the Buffalo Museum of Science, NY, USA, and Jeffrey Schwartz of the University of Pittsburg, PA, USA, coauthored a paper (John R. Grehan and Jeffrey H. Schwartz. Evolution of the second orangutan: phylogeny and biogeography of hominid origins. Journal of Biogeography, 2009 DOI: 10.1111/j.1365-2699.2009.02141.x) putting forward the idea that humans evolved from the orangutans. Schwartz had already championed this cause in his 2005 book The red ape: orangutans and human origins, and Grehan has published about this same idea in 2006 (more below).
In their 2009 article, they argue that morphology shows that humans and orangutans share 28 unique physical traits compared to 2 with chimps and 7 with gorillas. Another 7 features are shared with all three apes, and finally, chimpanzees and gorillas share 11 features, placing them closer together.
Furthermore, the DNA record is patchy with large gaps in the sequences, so it can't be used conclusively to support a common ancestry with chimps.
Another factor that is seldom taken into account, is that there are no fossils linking humans with chimpanzees.
Both authores propose that humans and orangutans shared a common ancestor, in Asia, that originated the organgutans in Southeast Asia, and then migrated west across Asia, to Africa and Europe some 12 million years ago when this region was forested and formed a single ecosystem. Then, the western branch evolved into a group of apes that later became extinct, and, the first Homo individuals.
Since the fossils of apes in Africa are not older than 500,000 years, and there are older fossils in Europe, the orthodox viewpoint is that the apes originated in Africa, migrated to Europe, and from there to Asia (the orangutan ancestors), and then, returned to Africa to generate the African apes and humans. The authors argue that this is too complicated to be true.
The paper also compared Australopiths and orangutans, who share 8 traits in common and with early humans, and 7 traits between themselves.
Grehan wrote, in his earlier work, in 2006 (Mona Lisa smile: The morphological enigma of human and great ape evolution. The Anatomical Record Part B: The New Anatomist. 289B. 139-157. 10.1002/ar.b.20107.) that the similar shape (morphology) of 28 human and orangutan features vs. only eight between humans and chimpanzees "suggests there is very little in morphology to support a unique common ancestor for humans and chimpanzees... 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." Grehan then examines similarities in detail, such as male mustache and beard, concealed female ovulation, long pair-bonding and prolonged mating, tool use, art, and "house" building.
The article includes the following phylogenetic tree:
My last post noted that the PtERV 1 repeat found in all African apes (chimps, gorillas, bonobos), and many Eurasian ones, is completely absent in orangutans and humans. This could imply a common trait in both species that shielded them from this retroviral infection, or even an isolation in Eurasia for both species that preserved them from the infection.
Interestingly, the DNA of orangutans differs from human and chimpanzee DNA, they split around 12 million years ago from the branch leading to us and chimps yet have undergone fewer mutations than the latter species: " the orangutan has evolved much more slowly than chimpanzees and humans. The orangutan genome has fewer large DNA sequence structural rearrangements than its chimpanzee and human counterparts. Large genome structural rearrangements are DNA mutations that result in large genomic segments being duplicated, deleted, inserted or inverted... "In terms of evolution, the orangutan genome is quite special among great apes in that it has been extraordinarily stable over the past 15 million years"" (Source), chimpanzees and humans "lose and gain new genes at twice the rate of orang-utans." (Source). This is indeed odd. Could it be possible that the split date has been calculated wrong? If the split date was more recent, say 6 million years ago, their mutation rate would be the same as that of the other great apes. It would also bring them closer to us.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2026 by Austin Whittall ©
No comments:
Post a Comment