Fossilized bacteria have been found in rock 3.5 billion years old in Africa

A primate of this period, at ease both in the trees and on the ground, is probably the common ancestor of gorillas, chimpanzees and humans

Various species of ape develop the habit of walking upright on two feet

Certain primates, in eastern and southern Africa, are by now sufficiently like humans to be classed as hominids

Ardi, the earliest known individual of partially human type (or hominid), is of the species Ardipithecus, in the Awash valley region of Ethiopia

Two or three hominid individuals, probably Australopithecus Afarensis, walk upright through volcanic ash at Laetoli, 30 miles south of Olduvai Gorge, and their footprints are preserved within subsequent ash deposits

A female of the species Australopithecus Afarensis (nicknamed Lucy when her skeleton is found), lives in the Afar Depression in Ethiopia within 50 miles of where her predecessor Ardi was unearthed

The earliest known chipped stone tools are made by hominids at Gona, in the Awash Valley in Ethiopia, close to the region where Ardi and Lucy lived many millennia earler

The Palaeolithic era or Old Stone age begins, characterized by hominid and human use of unpolished chipped stone tools

Australopithecus Boisei lives in East Africa, and is possibly the first hominid species to use stone tools

The earliest Palaeolithic era, known as the Lower Palaeolithic, covers the period before the emergence of homo sapiens in the form of Neanderthal man

Creatures of the genus Homo, classified as early modern humans, are living in east Africa

Homo Habilis, the earliest widely acknowledged species in the genus Homo, lives in East Africa with a brain size much greater than the contemporary Australopithecus Boisei

A hominid, nicknamed Twiggy and thought to be in the species Homo habilis, is living in East Africa

A species of human in east Africa, Homo erectus, is probably the first identifiable ancestor of modern man

Homo erectus, moves out of Africa and begins to spread through Europe and Asia

A Homo erectus boy, aged about ten, lives near Lake Turkana in Kenya and dies at Nariokotome

Humans in coastal areas of South Africa extend their diet to include shellfish and other marine sources of food

The last common ancestor of modern humans and Neanderthals evolves in Africa (possibly the species known as Homo Rhodesiensis)

Fire is used in China by Peking man, and may have been in use much earlier in Africa

A possible second migration from Africa begins, involving at some time the ancestors of modern man, Homo sapiens sapiens

Neanderthal man is by now well established in Europe and Asia, probably having evolved after his ancestors left Africa

In the Blombos cave in South Africa stones are engraved with patterns of lines, either decorative or practical (as a form of tally)

Somebody in southern Africa cuts grooves in a baboon fibula (the Lebombo bone), suggesting the possibility that prehistoric humans may have had tally-keeping skills

Painted and engraved images, on the rock face in a cave near Twyfelfontein in Namibia, date from this period