paleontology9: The rise of primates and onto our origin (v1.0)

A class of placental mammals called primates first emerged in the fossil record about 55 million years ago. This essay traces their origins and evolution all the way to the hominins which we belong to. The narrative then continues in my set of paleoanthropology essays.

Primates (also called anthropoids) are characterized by grasping hands and feet, nails, and stereoscopic vision. It is believed they originated in Asia and moved into Africa early. A relative of Primates with a common ancestor with primates are Prosimians who are typically nocturnal and often are insect eaters that include lemurs, lorises and tarsiers. The fossil for the first primates is from 55 million years ago. They started out as tree climbing, as active during the day, as eating a flexible mixed diet including leaves and fruits, as with a larger brain, as mostly single birth, and as living in groups. These characteristics gave them more complex behaviors including social ones. The emergence of primates was a major evolutionary transition.

Monkeys are a side evolutionary branch in primates. The first monkeys emerged about 26 million years ago. New world monkeys from the Americas were incredibly diverse. Old world monkeys from Europe/Africa/Asia are also remarkably diverse and include baboons, macaques, and langurs. They both came from a common ancestor from the Eocene period about 35 to 55 million years ago. The continents were separated by water bodies. How did the new world monkeys get to south America? One theory is that logs from trees may have had enough sustenance for them to get across the much smaller Atlantic of that time. Rodents made it across the same way.

Hominids (the great apes) are primates that include the gorilla, orangutan, chimpanzee, bonobo, and the Homo species of which we are the only surviving descendants. The hominoids are all the living great apes, their fossil relatives and living humans. The transition to the Great Apes was a major evolutionary transition. They first emerged about 10-13 million years ago. Gibbons had branched off about 16 to 20 million years ago, while old world monkeys had branched off 26 million years ago. The apes from Africa in the early Miocene (23 million to 5.3 million years ago) dispersed into Asia and Europe. Let us compare great apes to old world monkeys, their nearest relative. Apes have more mobile shoulders to move around. Apes have more grinding teeth. Apes have a relatively long lifespan and a long time to grow up. Apes have a long birthing interval (interval between births).

Hominins are living humans and their extinct relatives. The Orangutans branched off from the Hominids about 10 to 13 million years ago. Gorillas branched off about 6 to 9 million years ago. Chimps and bonobos branched off about 4 to 7 million years ago (Chimps split off from bonobos about a million years ago). Hominins emerged after that.

The story now continues with the origins and evolution of Hominins in the first essay of the paleoanthropology series. Here is the link.

https://jaykasi.blogspot.com/2023/10/when-and-where-did-homo-genus-first.html

I will briefly touch on various mass extinctions before the final conclusion. There were five big ones. 

1. Ordovician-Silurian Extinction: 85% of all life - mostly marine - died out. A huge, buried crater in New South Wales may possibly be the asteroid impact cause but not confirmed. (440 mya)
2. Devonian Extinction: Many tropical marine species went extinct. (365 mya)
3. Permian-Triassic Extinction: This largest mass extinction event in Earth's history affected a range of species, including many vertebrates. 90% of marine species and 70% of terrestrial species dying out. This is believed to be due to flood basalt volcanic eruptions which created the Siberian Traps, that changed the climate and acidified the ocean. Today, the area is covered by about 3 million sq mi of basaltic rock, with a volume of around 1 million cu mi. (250 mya)
4. Triassic-Jurassic Extinction: The extinction of many other vertebrate species on land allowed dinosaurs to flourish. Likely caused by ecologic catastrophe including by volcanic eruptions. (210 mya)
5. Cretaceous-tertiary Extinction: (65.5 mya). Triggered by a huge asteroid hitting earth in the Yucatan peninsula. Dinosaurs and flying reptiles and most marine reptiles died out. Mammals dominated after that. 

This completes my series of essays on evolution. I have covered both from the dawn of life to hominins and separately from hominins to modern humans. All of the above life evolution essays seems to demonstrate an almost doggedly systematic and almost purposeful sequence of events in a seemingly intelligent way. Life is seemingly intelligently put together. There are intermittent mass extinction events that seems almost like corrections to improve evolutions direction. But 4 billion years is a very long time for life on earth. I cannot wrap my head around such scales, and many see that as enough time for the remarkable changes that took effect through the laws of natural selection for life.