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Orangutan–human last common ancestor

Model of the speciation of Hominoidea over the past 20 million years.

The orangutan–human last common ancestor is the last species that the subfamilies Homininae and Ponginae (i.e. the gorillachimpanzeehuman last common ancestor on one hand and orangutans on the other) share as a common ancestor. It is estimated to have lived 11 to 16 million years ago during the middle Miocene.[1][2][3]

Hominoidea (hominoids, apes)
Hylobatidae (gibbons)
Hominidae (hominids, great apes)
Ponginae
(Orangutans)
Homininae
Gorillini
(Gorilla)
Hominini
Panina
(chimpanzees)
Hominina (Humans)

Appearance and ecology

The orangutan–human last common ancestor was tailless, and had a broad flat rib cage. The orangutan–human last common ancestor had a larger body size, larger brain, and in females, the canine teeth had started to shrink like their descendants.[4]:201 Great apes have sweat glands in their armpit versus in their chest like lesser monkeys[4]:195

Orangutans have anterior lingual glands and sparse terminal hair like the hominines. [4]:193

Terminal hairs are those hairs that are easy to see. As compared to the tiny light colored hairs called Vellus hairs. Certainly there is some correlation with the size of the mammal. The larger the mammal the fewer terminal hairs.[4]:195

The apical lingual glands are special glands of the endocrine system. Near the tip of the tongue on the underside are a pair of glands that secrete proteins and mucus. These are only found in the great apes so it is understood that the last common ancestor would also have these.[4]:195

With regard to the skull this is an example where humans share more in common with orangutans than with later great apes. We have two small ridges, one over each eye called superciliary arches.[4]:229

Orangutan skull showing superciliary arches similar to humans

The great apes other than humans and orangutans have a structure called the Supraorbital torus which is a continuous ridge of bone that goes over both eyes.[4]:229

Gorilla skull showing Supraorbital torus

Stem-orangutans and proof of European migration

Several discoveries of fossil humans have been reclassified as Stem-orangutans such as Yuanmou Man.

A stem group is a term in cladistics that describes a pan-group minus the crown group itself (and therefore minus all living members of the pan-group). In other words, it is a group of the primitive relatives of the crown groups but does not include the last common ancestor of the crown group. All members of a stem group are extinct.

Different genuses of dryopithecines have been discovered and are an extinct sister clade of the great apes.[4]:226. These discoveries help support the theory that the orangutan–human last common ancestor existed before 8 million years ago. Dryopithecines was first uncovered in France and it had a large frontal sinus which ties it to the African great apes.[5] Orangutans which are only found in Asia do not.[5] They did have thick dental enamel another ape-like characteristic.[5]

These discoveries also back up the theory that the closest relatives of humans evolved in Africa. It contradicts the alternative theory that Homininae were originally an Asian line which later recolonized Africa after the Great Apes went extinct in Africa.[6]

17 million years ago apes show up in Europe in the fossil record. During the early Miocene Europe and Africa were connected by land bridges over the Tethys Sea. An ancestor to the Great apes moved across a land bridge and 12.5 million years ago modern great apes show up in the fossil record in Europe and Asia.[7] This migration left the only living great ape in Asia; the orangutan.[5]

During the later Miocene the climate in Europe started to change as the Himalayas were rising and European became cooler and drier. About 9.5 million years ago tropical forest in Europe was replaced by woodlands which were less suitable for Great Apes and the Great Apes left Europe and went back to Africa to later evolve into Homininae to (yet again) leave Africa millions of years later.[5]

References

  1. ^ Jha, Alok (November 19, 2004). "Ape discovery fills gap in evolutionary jigsaw". The Guardian. Archived from the original on May 9, 2015. Retrieved May 8, 2015.
  2. ^ "Ancient Ape Discovered: Last Ape-Human Ancestor?". National Geographic News. November 18, 2004. Retrieved May 8, 2015.
  3. ^ Hansford, Dave (November 13, 2007). "New Ape May Be Human-Gorilla Ancestor". National Geographic News. Retrieved May 8, 2015.
  4. ^ a b c d e f g h Kane, Jonathan; Willoughby, Emily; Michael Keesey, T. (2016-12-31). God's Word or Human Reason?: An Inside Perspective on Creationism. ISBN 9781629013725.
  5. ^ a b c d e Wayman, Erin. "Did Africa's Apes Come From Europe?". Smithsonian. Archived from the original on April 4, 2019. Retrieved April 4, 2019.
  6. ^ Kunimatsu, Y.; et al. (2007). "A new Late Miocene great ape from Kenya and its implications for the origins of African great apes and humans". Proceedings of the National Academy of Sciences. 104 (49): 19220–19225. doi:10.1073/pnas.0706190104. PMC 2148271. PMID 18024593.
  7. ^ Dawkins, Richard; Wong, Yan (2016). The Ancestor’s Tale. ISBN 978-0544859937.

See also