Serengeti national park: High plains drifter Serengeti Story: Life and Science in the World's Greatest Wildlife Region. By Anthony Sinclair. Oxford University Press; 270 pages; $34.99 and £18.99. NESTLED between the two arms of east Africa's Great Rift Valley sits a vast plain on which roams an extraordinarily rich diversity of life. Just south of the plain lies the age-old Olduvai Gorge, near where two-legged hominids left footprints in the ash some 3.6m years ago - aeons before their descendant, Homo sapiens, marched out of Africa to encircle the planet. For anyone who has seen this plain, it is hard not to believe that on his way out mankind left behind something of his soul. The plain is called Serengeti, from a Maasai word for "great open space," and there are several ways to tell its story. Anthony Sinclair is a scientist who has worked there intermittently since 1965 recording the movement and behaviour of a range of animals - from the aardvark to the zebra. He arrived to study the migration of birds, moved rapidly on to buffalo before focusing on the wildebeest or gnu, a bizarre bearded antelope; its migration is central to the Serengeti's ecosystem. The book recounts how he made his remarkable scientific discoveries. For example, to have the best chance of survival about 90% of the wildebeest give birth within a one-month period, and hence need to conceive within a similarly short space of time. Mr Sinclair asks how they synchronise this mass mating, and then, in trying to find the answer, discovers that the beasts" conception period is linked to the lunar cycle; it shifts back ten days each year for three years and then leaps forward by a month. This is a tale of hope. The book documents the Serengeti's remarkable resilience, the close interdependence of its species and their recovery from disasters ranging from the rinderpest virus, which badly affected the buffalo and wildebeest populations before the 1960s (but left the zebras untouched), to the devastating drought of 1993 and the poaching of the 1990s, from which the black rhino, among other species, may not recover fully. The plain's populations fluctuate wildly, and probably always have. The elephant, for instance, was abundant in the area in the 1860s until the industrialising West's demand for billiard balls and piano keys encouraged the ivory trade. By 1913 a hunter called Stewart Edward White could find no elephants at all on the plain. Yet by the 1960s their numbers had recovered to such an extent that there was talk of a cull. And this same cycle has been repeated over the past 30 years. The author never entirely sheds his academic persona. "Serengeti Story" has more than 300 footnotes. But it is also, as Mr Sinclair says, "a book of stories," and although the stories consist mostly of tales of human discomfort in the presence of animals, this is no dry textbook. For this (non-scientific) reader at least, it maintains the balance well. At the centre of the book is a question: how can man ensure that such a place continues to exist? Mr Sinclair is reservedly optimistic, rightly full of praise for Tanzania, which has dedicated 14% of its land to national parks, reserves and conservation areas. But this richly diverse ecosystem is forever on the tipping point to irreversible decay. No sooner does one threat fade than another looms. The latest is a project to build a tarmac road across the north of the park, a plan that risks leading to increased poaching of animals and more human settlement and tree loss within the park. The plan is currently on hold while the government seeks international funding for a longer detour round the south of the park. For Mr Sinclair the main lesson to be drawn from his years in the Serengeti is that "nothing is ever secure against human greed." The price of this sanctuary for the soul, as it is for liberty and peace, seems to be eternal vigilance - by men like Anthony Sinclair and Tanzania's park wardens.