Prehistoric World

20-10 million

During the Early and Middle Miocene eras, dating between twenty and ten million years ago, Africa had a much higher annual rainfall level than today. A single super-rainforest covered most of the continent from shore to shore. A hominoid (primate) ancestor common to all living apes and humans lived in the trees of this super-rainforest.

Africa first became connected to Eurasia around 18 million years ago, causing major geological upheavals, and transforming formerly flat landscapes by pushing up some of the world's youngest mountain ranges: the Pyrenees, the Alps, and the Zagros mountains, as well as the mountains and rift valleys of East Africa. Geographical transformations were accompanied by gradual climatic and environmental changes which may even have triggered the emergence of the first specialised hominoids.

Proconsul africanus

The very earliest known representatives of the hominoids have been found only in Africa and were very different from living apes and humans. The oldest finds belong to a group of species in the genus Proconsul. Fossils of Proconsul have been found in Early Miocene deposits 22 million years old in Kenya, and along the rift valley, although it probably originated rather earlier, between 25 and 28 million years ago.

Proconsul's skeletons are described as generalised in that it shows none of the particular features such as thickened tooth enamel or adaptation for knuckle-walking which characterised the later apes. It was adapted to living in trees and was about the size of a gibbon.

Proconsul suffered somewhat during Africa's collision with Eurasia. Volcanic activity reached a peak 18 million years ago, especially in East Africa. The Kisingiri volcano erupted, apparently with a pyroclastic flow, killing whole populations of Proconsul which lived in an environment which was semi-arid, covered mostly in dry, deciduous, single-canopy woodland, with some evergreen forest in restricted, low-lying areas.

Despite repeated volcanic activity around this period, the species persisted into the Middle Miocene (15 to 10 million years) when it overlapped with Kenyapithecus.

20,000,000

Ugandapithecus major

Another early hominoid also existed in Africa around 20 million years ago. Ugandapithecus major is known to have lived around the site of a now-extinct volcano in Uganda's remote north-east Karamoja region.

Scientists say preliminary analysis of a single specimen discovered there showed that the tree-climbing herbivore was roughly ten years old when it died. The skull was about the same size as that of a chimp, but its brain was smaller.

Ugandapithecus major was previously classified as Proconsul major, and some areas of academia continue to argue against the reclassification.

17,100,000

Engelswies hominid

At about 17.1 million years, probably as soon as a land bridge was formed between Africa and Eurasia, some hominids migrated out of Africa. Once in Eurasia, they eventually found a fertile valley in what is now south-western Germany, north of the Alps, the Engelswies hominid being perhaps one of the very first Eurasian hominoids to appear. The partial upper third molar of the Engelswies example has been tentatively attributed to Griphopithecus.

The region apparently had its own microclimate with a mean temperature of 20ºC, about 11ºC above present day conditions there. There was a swamp to the south of a lake which was full of reed beds, with a coastline of deciduous trees, palm trees (amongst them the climbing rattan palms), lianas, ferns and grasses. To the north was a slope covered by an evergreen forest.

These Engelswies hominids eventually died out as conditions dried and cooled, but they were the first in a series of migrations out of Africa.

15,000,000

Kenyapithecus africanus

The appearance of Kenyapithecus between 15 to 11 million years ago marked the point at which some specialisations began to appear. This hominoid also lived exclusively in the rainforests of Africa's Rift Valley, and showed modifications in the teeth and limb bones, making them more like those of the living great apes. It may have been a knuckle-walker, showing a stage of progression from tree-living to upright walking.

Kenyapithecus africanus can be regarded as being part of the combined great ape and human group but cannot be linked directly to any one of the living hominoids.

However, evidence has emerged which strongly suggests that Kenyapithecus is not one genus but two.

Kenyapithecus wickeri appears to have migrated out of Africa at the same time as many other species and lain the roots of the later European apes. Kenyapithecus africanus has been rechristened by some scholars as Equatorius africanus, because the Equator is where all its remains have been discovered. Louis Leakey was the first, in 1961, at Fort Ternan in Kenya.

14,000,000

Ramapithecus & Sivapithecus

By around 14 million years ago there were other hominoid variations in existence, and these had migrated out of Africa, with some representatives spreading east across into the Asian continent. By 14 to 11 million years ago Ramapithecus and Sivapithecus were in Anatolia and Pakistan (and had reached South Asia by 8 million years ago where a group of one of them evolved into the enormous Gigantopithecus).

They are closely related to the orang-utan, and differed from each other only in size, suggesting that they were also closely related to each other and may perhaps be males and females of the same species.

Both also share some of the characteristics of Kenyapithecus, as well as particular features which show they must be related exclusively to the orang-utan and not to humans. This evidence supports the view that the orang-utan was the first to split away from the general hominoid pool in Africa.

14,000,000

Dryopithecus

Dryopithecus emerged in Africa and Europe at around the same time as Ramapithecus, and persisted in Central and North-Western Europe into the Late Miocene.

The connection between the two continents was more direct than it is today (see map, above). Much of the bulk of Southern Europe was still a relatively thin corridor of land no more than twice the width of modern Italy in most places, while the Tethys Sea was twice as big as the Mediterranean Sea which it would later become.

Dryopithecus remains have only been discovered in the past forty years or so (as of 2015).

The creature, which was more like Proconsul, was thought highly unlikely to be related to any of the living hominoids, while there was a suspicion that it could have a place in early hominid ancestry. Now, though, it seems to have been added into a larger Dryopithecine genus of apes with the link to hominids being discarded.

13,000,000

Nyanzapithecus alesi

A 13 million year-old infant's skull, discovered in Africa in 2014, came from a new species of ape which may not be far removed from the common ancestor of living apes and humans.

The tiny find, about the size of a lemon, was one of the most complete skulls known of any extinct ape which inhabited Africa, Asia, or Europe between 25-5 million years ago. Comparisons with other African ape fossils indicate that the infant's skull belonged to a new species which researchers named Nyanzapithecus alesi. Other species in this genus, previously known from jaws and teeth, date to as early as around 25 million years ago.

N alesi's tiny mouth and nose, along with several other facial characteristics, made it look much like small-bodied apes called gibbons. Faces resembling gibbons evolved independently in several extinct monkeys, apes, and their relatives, according to the researchers. The same probably held for N alesi, making it an unlikely direct ancestor of living gibbons.

Several of the infant skull's features, including downsized semicircular ear canals, connect it to a poorly understood, 7-8 million year-old ape called Oreopithecus. Fossils of that primate, discovered in Italy, suggest that it walked upright with a slow, shuffling gait. If an evolutionary relationship existed with the older N alesi then the first members of the Oreopithecus genus probably originated in Africa, although that has yet to be proven.

Without any lower-body bones for N alesi, it's too early to rule out the possibility that Nyanzapithecus gave rise to modern gibbons and perhaps Oreopithecus as well. Despite the age and unprecedented completeness of the new ape skull, no reported tooth or skull features clearly place N alesi close to the origins of living apes and humans.

10-7 million

Geological changes

At around 10 million years ago a large number of the first ape-like groups had blossomed into a huge radiation of species which reached across Europe and much of Asia. Over subsequent time the majority of them became extinct, mostly due to climate changes and extensive glaciation.

Further geological upheavals now occurred. The sub-continent of India had been creeping northwards across the Indian Ocean since about 220 million years ago, during the break-up of the super-continent of Pangea. It finally started to collide with Asia around 50 to 40 million years ago, but the effects of that collision became serious around 10 million years ago.

The collision had gradually been forming a crunch point in the form of the Himalayas. Now this mountain rage reached a height which began to impact upon weather patterns, causing them to change. Massively increased rainfall in India (the Monsoon) stripped the air of moisture so that the air currents which reached Africa were no longer wet, but dry.

In East Africa this caused drier conditions during the Late Miocene sub-epoch (10 to 5 million years ago). Temperatures began to increase, resulting in a spread of grasslands as the super-rainforest began to die back over the next five million years. Animals had to adapt in response to these changes.

Between 7.0 to 5.8 million years ago, hominid transitional species appeared as the ancestors of man and chimpanzee divided. The term 'hominid' refers to the family of primates which includes all species on the 'human' side of the evolutionary tree after that split. The chimpanzee's ancestors remained living in the remnants of the great forests, while early hominids placed an increasing reliance on surviving outside the shrinking forests.

Unfortunately, conditions in Africa between around 11 million to 5 million years ago were very detrimental to the preservation of fossils. There are very few finds being made from this period, and very little evidence from which to build up an accurate picture of evolutionary events. However, some finds have been made more recently and the science behind their analysis has improved...