Mammalian and Human Evolutionary Timeline

I did some work for Peterborough Museum and looked at the evolution of mammals and then humans so I am going to do a post on a timeline of this evolution.

Mammal Evolution:
256 Ma - Wuchiapingian age, Lopingian epoch, late Permian period, Palaeozoic era:

Dimetrodon, an example of a pelycosaur. Image credit
extinctanimals.org

Shortly after the first appearance of reptiles in the Carboniferous period, two evolutionary branches split. The first branch is the Sauropsids, which later become the birds and reptiles of the modern day, the first example of the sauropsid is the Hylonomus. Synapsida is the other branch which gives rise to the mammals.

Both of these branches have temporal fenestrae (openings) behind the orbit which allows for larger jaw muscles. 

The earliest mammal-like reptiles are the pelycosaurs. These animals were the first to have temporal fenestrae. The pelycosaurs gave way to the therapsids, the direct descendants of mammals. The temporal fenestrae of therapsids are larger and more mammal-like than pelycosaurs.  

220 Ma - Norian age, Upper Triassic period, Mesozoic era:
The cynodonts were a subgroup of therapsids and bore the most mammal-like features; it's jaws for example resembled the modern jaws of mammals. It is likely that with in the cynodonts, the direct ancestor to all mammals can be found. 

Artist's impression of Juramaia sinensis alongside
skeleton. Image credit Mark A. Klingler

From Eucynodontia came the first mammals. These were very small, shrew-like animals that fed on a diet of insects. They evolved the neocortex region of the brain and so it is unique to animals.

160 Ma - Oxfordian age, Upper Jurassic period, Mesozoic era:
The earliest known mammal fossil of Juramaia sinensis comes from the Jurassic period, this is the first true mammal that we know of.

100 Ma - Cenomanian age, Upper Cretaceous, Mesozoic era:
The last common ancestor of mice and humans is found here in the Cretaceous period.

Primate Evolution:
85 to 65 Ma - Santonian to Maastrichtian age, Upper Cretaceous, Mesozoic era:
A group of small, insect eating mammals called Euarchonta evolved at the end of the late

Reconstruction of a group of Plesiadapis. Image credit
odec.ca

Cretaceous. This group would give rise to primates, treeshrews and lemurs. Plesiadapis is an animal from the subdivision primatomorpha and lived on the lower branches of trees feeding on fruits and leaves. Plesiadapiformes are very likely to contain the species that are the ancestors of the primates.

63 Ma - Danian age, Palaeocene epoch, Palaeogene period, Cenozoic era:
Primates diverge into strepsirrhini, wet nosed primates, and haplorrhini, dry nosed primates.

Strepsirrhini contains ancestors to lemurs and lorises. The haplorrhines include prosimian tarsiers, simian monkeys and apes. Haplorrhini metabolism lost the ability to make its own Vitamin C, this means that the descendants had to include fruit in their diet. 

30 Ma - Rupelian age, Oligocene epoch, Palaeogene period, Cenozoic era:
Haplorrhini splits into two; platyrrhini and Catarrhini. 

Platyrrhini are new world monkeys that had prehensile tails. It is believed that they migrated to South America, floating on a raft of vegetation is one possible hypothesis for this migration. 

25 Ma - Chattian age, Oligocene epoch, Palaeogene period, Cenozoic era:

Replica skull of Proconsul africanus. Image
credit Don Hitchcock

Catarrhini splits into two groups; old world monkeys, ceropithecoidea, and apes, hominoidea. 

The trichromatic vision had its genetic origins in this period. Proconsul africanus is a possible ancestor of great and lesser apes, including humans.

Hominidae Evolution:
15 Ma - Langhian age, Miocene epoch, Neogene period, Cenozoic era:
Hominidae ancestors speciate from the ancestors of gibbons.

13 Ma - Serravallian age, Miocene epoch, Neogene period, Cenozoic era:
Hominidae ancestors speciate from the ancestor of Orang-Utans. 

The common ancestor of the great apes and humans is believed to be Pierolapithecus catalaunicus. Like humans it had a wide, flat rib cage, a stiff lower spine, flexible wrists and shoulder blades on its back rather than its side. 

10 Ma - Tortonian age, Miocene epoch, Neogene period, Cenozoic era:
The human lineage and the genus of Pan (chimpanzees and bonobos), speciates from the ancestors of gorillas.

7 Ma - Messinian age, Miocene epoch, Neogene period, Cenozoic era:
Hominina speciate from the ancestors of the chimpanzee. 

In the first two years of life, ancestral humans and chimpanzees have a larynx that repositions itself to between the pharynx and lungs; a feature that enabled speech in humans.

3.6 Ma - Piacenzian age, Pliocene epoch, Neogene period, Cenozoic era:
Australopithecus afarensis is evidence for full time bipedalism in early hominids. this ancestor had reduced canines and molars, although still larger than modern humans.

A study of the lower vertebrate of Australopithecus afarensis suggests that in females, changes had been made so that bipedalism could be sustained throughout pregnancy.

3.5 Ma - Piacenzian age, Pliocene epoch, Neogene period, Cenozoic era:
Kenyanthropus platyops is a possible ancestor of Homo, and it emerges from the Australopithecus genus.

3 Ma - Piacenzian age, Pliocene epoch, Neogene period, Cenozoic era:
A loss of body hair takes place in Australopithecines while they evolve on the savannahs of Africa.

Homo Evolution:
2.5 Ma - Gelasian age, Pleistocene epoch, Quaternary Period, Cenozoic era:
Appearance of the genus Homo. Homo habilis and Homo ergaster lived side by side in the lower Pleistocene. The first stone tools were used here.

1.8 Ma - Calabrian age, Pleistocene epoch, Quaternary period, Cenozoic era:
Homo erectus evolves in Africa. Homo erectus resembles more modern day humans, the forehead is less sloping and the teeth are smaller.

Homo georgicus is the oldest hominid fossil outside of Africa, showing that they had the ability to travel long distances, probably following herds of animals.

The evolution of dark skin came with the loss of hair. The brain evolved to be larger and therefore tool crafting was more successful. They could then hunt bigger prey such as wild horses.

1.2 Ma - Calabrian age, Pleistocene epoch, Quaternary period, Cenozoic era:
Homo antecessor may be a common ancestor of humans and Neanderthals. Humans share 99% of their DNA with the now extinct Neanderthals.

600,000 years ago - Middle Pleistocene epoch, Quaternary period, Cenozoic era:
Homo heidelbergensis was found in Italy, it had a larger brain case and was therefore more intelligent than its ancestors, but more muscular than modern humans.

200,000 years ago - Middle Pleistocene epoch, Quaternary period, Cenozoic era:
Earliest fossils of anatomically modern humans found in Ethiopia dating back 0.2 Ma.

60,000 years ago - Upper Pleistocene epoch, Quaternary period, Cenozoic era:
Homo sapiens migrate out of Africa. Homo sapiens interbreed with the Neanderthals that they encounter.

50,000 years ago - Upper Pleistocene epoch, Quaternary period, Cenozoic era: 
Homo sapiens migrate to Southern Asia.

40,000 years ago - Upper Pleistocene epoch, Quaternary period, Cenozoic era:
Homo sapiens migrate to Australia and Europe. The European Homo sapiens known as Cro-Magnon.

25,000 years ago - Upper Pleistocene epoch, Quaternary period, Cenozoic era:
Neanderthal lineage becomes extinct.

20,000 to 10,000 years ago - Upper Pleistocene epoch, Quaternary period, Cenozoic era:
Homo floresiensis dies out, leaving Homo sapiens as the only species of Homo still surviving. Evolution of light coloured skin in Europeans took place around this time.