London to Dar es Salaam

The marked edge of the Rift Valley steeply falling away to open scrubland is clearly visible from the air and can be traced down the length of the Horn of Africa.

A diagram of the Earth's tectonic plates - forces tearing apart the African plate (shown as red arrows) act between the yellow and orange segments: the Great Rift Valley is along this boundary.

The lakes of the African Rift Valley exhibit wide variations in water colour. From left to right the lakes are: Lake Upembe, Mwaru, Tanganyika (largest) and Rukwa.

The massive Silali Crater is just to the north of Lake Baringo and was formed by a similarly huge volcano, now also extinct - a line of these craters can be seen along the Rift throughout its length.

Sunrise over Lake Baringo, with Ol Kokwe, an extinct volcanic crater in the background. This is one of the most northernly Kenyan Rift Valley lakes.

Nyiragongo volcano, on the eastern edge of the DR Congo, is one of the most active volcanoes on the East African Ridge - with Nyamuragira, the two volcanoes cause 40% of activity along the ridge.

Lake Bogoria, in Kenya, sits above a volcanic hot spot on the East African Ridge. As well as being a haven for wildlife, it exhibits hot springs and geysers due to the hydrothermal activity.

An aerial view of the crater of Mount Longonot, part of the Kenyan chain of volcanoes marking the East African Rift.

The Crater Highlands, part of the East African Rift running through Tanzania. Volcanoes highlight the edge of the plate.

This satellite image of north-east Africa shows the Great Rift Valley curving in an arc from the Gulf of Aman in Ethiopia (top right) to northern Kenya (bottom of image).

The Elmenteita Badlands, a range of volcanoes and craters to the south of Nakuru, are clearly seen in this satellite image of the area and the Rift.

A map showing the Afar Triple Junction: the tectonic plates making up the Earth's surface are being torn along these lines. The East African Ridge is part of this and can be seen running through Africa.

The steep cliffs and pronounced geological formations of the Great Rift Valley are a key part of the dramatic beauty of this unique landscape.

A Maasai mother and child - many generations of the same family will grow up in the same kraal (settlement) with women looking after children too young to tend livestock.

A Maasai village - huts are arranged in a traditional circular kraal, with a surrounding fence of acaia thorns used to prevent lions attacking the cattle which are held in the centre overnight.

Maasai warriors dancing adumu - traditional dancing competitions involves the male warriors jumping from standing position to see who can reach the greatest height, whilst the others sing.

Maasai herders with livestock, dressed in traditional shúkà robes, which are usually red or striped patterns and worn draped across the body.

1882 - A map detailing known native routes to the Maasai country. Mount Kilimanjaro can be seen in the centre of the map.

The son of a Maasai Chief - white is a holy and revered colour in Maasai culture reprenting cow's milk and life, whilst yellow represents hospitality and guests.

19th century - Maasai moran (warriors) with spears at Mianzini, northern Tanzania.

1979 - A Maasai child peeking out from within his house in the Maasai Mara, Kenya.

Nongishu Kingi and her family in the Kingi boma - Nongishu helps to support her family by selling bracelets and beadwork at a local market.

Maasai women in Engaresero village selling their beadwork to tourists - many can no longer rely solely on their cattle and are keen to bring in additional income to support their families.

Maasai women make repairs to the roof of a house - it is the women's responsibility to construct houses from a mixture of mud, sticks, grass, cow dung, human urine, and ash.

A Maasai bride in traditional jewellery and costume - Maasai are polygamous and this women will marry not just her husband but his entire "age group" of warriors.

1907 - Maasai moran (warriors) with spears and shields.

A collection of reconstructed Australopithecus africanus skulls and jaw-bones based on finds from the Great Rift Valley.

A view over Lake Naivasha, north of Nairobi and part of what is considered to be the "cradle of humanity" within the Great Rift Valley.

An artist's reconstruction of what "Lucy" may have looked like - we can see similarities to ourselves in this representation, bringing evolution to life.

An artist's reconstruction of our Homo egaster ancestors - further along the evolutionary chain than "Lucy", you can see a growing similarity to modern humans.

The Afar Depression, the starting point of the East African Ridge and the home of the well-preserved remains of the Australopithecus afarensis skeleton "Lucy".

A cast of "Lucy's" skeleton - our Australopithecus afarensis ancestor found in the Great Rift Valley and believed to be 3.2 million years old.

A map of the fossil sites and spread of the ancestral species Australopithecus and Paranthropus across Africa. These range in age from 1 million to 4.3 million years old.

Three dimensional models of modern human footprints compared with those of our ancestors as reconstructed through fossil evidence, through evolution walking on two legs not four.

A reconstruction of "Lucy's" skeleton at the Senckenberg-Museum in Frankfurt - she was the first evidence of a sub-species that walked upright as humans do today.

A scientist's model of an Australopithecus afarensis female, based on the "Lucy" fossils found in the Great Rift Valley in Ethiopia.

A reconstruction of the skull of a Australopithecus afarensis ancestor, based on the "Lucy" fossils.

A satellite image from the International Space Station of the Awash Valley in Ethiopia, part of the Great Rift Valley and where "Lucy" was found.

A schematic map showing the spread of humans as they evolved: our early ancestors spread out from their home in Central Africa to travel across the world over time (as shown by the coloured arrows).