Conservation Biology

Tuesday, August 29, 2006


Book Review: Out Of Africa’s Eden: The peopling of the world, by Stephen Oppenheimer.

Through the crash-course in human evolution from the discussion of Australopithecus anamensis, Australopithecus afarenis, and the functions and pressures theorised for the beginning of bipedalism and the expansion of the human brain, intellect and language, comes the romantic story of us. We as modern humans are one big family linked by the very substance which makes us who we are, DNA.

Although the book revolves around the science of mitochondrial DNA, passed down from mother to daughter, the suggestion that the Y-chromosomal DNA of men, that of the incorruptible small segment, could actually reflect greater resolution of time and geography than mitochondria DNA, is extremely interesting, and may even see a shift in future thinking regarding the historic movements of the human population.

The Out of Africa Hypothesis seems to drown out the shadow of the Multiregional Hypothesis in this book, which although honours the scientific relevance of those dwindling scientific communities, does so through an informative lay approach to understanding the genetics involved. One aspect, that of contemporary respect for alternative opinion, is however not honoured in this book. I feel that although a definite separation between Creationism and Darwinian theory should be observed, religious aspects should be respected equally to that of science, and neither should be dismissive of the other. It is clear from the author’s opinion that he is dismissive of Creationist theory, with specific reference to the following quote “We were not ‘put’ here fully formed, thinking, talking, and unique among animals.” The quoted sentence refers to the book of Genesis, when Man was put onto the Earth by God, who made him unique among animals, giving him dominion over everything he saw. As a studying scientist, but also a Christian by faith, I find this statement rather disrespectful and one which detracts from the essence of the book. In addition, the author makes repeated reference to biblical history and nomenclature for “ease of reading” throughout the book, which is somewhat ironic.

Ultimately it was destined for the human race to move out of Africa, since Africa was the cradle of mankind. The climate and the window period conducive to successful migration facilitated the successful migration of Homo erectus and later modern man into the rest of the world. The first exodus of humans out of Africa probably ended in disaster, as no genetic evidence survives that can substantiate their survival. The climate at the time of the first exodus of humans out of Africa suddenly became globally colder, an ice age, which locked up vast majorities of available water in polar ice-sheets, which turned once lush areas into desert. A good example of this is the Sahara desert, which would have trapped any attempts of migrating back South through what is known as the Northern corridor to more hospitable lands. Interestingly, it may also have been the Southward creeping of the North-polar ice-sheet which forced Homo nearderthalensis further into Europe before the appearance of modern humans in Europe approximately 50 000 years ago.

So, what about the Australians then? Apart from the speculation that there is still only one route out of Africa, the alternative route, the Southern Route, which gives evidence to the migration of humans out of Africa and through Asia and eventually South to Australia, reflects a more possible and ingenious migration route. The Northern route is well documented, however, what struck me was the interpretation of the Southern route, which seems to agree with my instinctive understanding of self-preservation. It is simply explained. With the onset of an ice age and generally drier conditions, food resources would have become notably scarce, in addition to water. Not only do most rivers run into the sea, but the sea shore itself can provide an alternative food source which can be taken advantage of. There is much evidence of sea food harvesting in South Africa and the Red Sea, and with a reduction in sea levels and a beach-comber come nomadic existence, it was only a matter of time before modern humans found themselves following the outline of the continents out of Africa, Asia and towards Australia. An interesting section in the book suggests that contemporary, more archaic human species, indigenous to Asia, may well have been the reason for a possible prolonged expansion from Africa. The author makes a valid point, and one which we need to remember as not anthropomorphic as some may suggests, modern humans today and modern humans then, share the infinite possibilities of their own thought processes, are ingenious, cultured, and survivors. Was Africa modern human’s territorial home, which he was happy with, and did possible scouting expeditions return with news of competition and therefore less-favourable conditions? Could we have moved out of Africa earlier than is suggested? The first Australians arrived on the new continent not only as the first placental mammals, but as a calculated progressive step taken as an opportunity at the last great ice age. Genetic evidence reveals support for this through multiple founding maternal genetic lines.

Modern Europeans are all descendant from humans from Asia who crossed over the green fertile strip corridor about 50 000 years ago. Again it was the fate of the climate, which facilitated the migration from Asia into Europe of modern humans. Without the warming of Southern Asia, creating improved monsoon conditions, modern humans may well not have arrived in Europe at this time, and the ultimate fate of the Neanderthals could well have been different.

Impressively, the author tackles the issue of cultural prejudice, which is something not only relevant to our time and place in South Africa, but something I did not expect to have resulted in historical indoctrination where the history of human development, and even the historical essence of being human, is often reflective of social opinion. The statement that “First impressions last” sums up this section in the book, which deals superficially, though concisely, with the problem of perceived ideas and assumptions of cultural supremacy among contemporary Homo species. Indeed, who are we to portray Homo neaderthalensis as inferior based on their technology and our own assumptions when their brains were in fact larger than ours, and our technology was almost equal to theirs for a vast period in time… This begs the question: Could what is seen as scientific fact, actually be scientific prejudice? Is scientific history as we know it actually scientific propaganda? It is sad to think that historically, Europeans particularly have seen their development as being superior and it is no surprise that the idea that they are descendant of those Africans who migrated into Asia was difficult to accept when this theory was put forward. The European story is most interesting as it displays the process by which the climatic conditions once again can have a primary impact on the direction and the definition of peoples. Climatic changes were responsible for the change in skin colour gradually from a dark melanised skin to a paler skin colour. The reason for this is relatively simple. Through some investigation I discovered that Our African ancestors and similarly our African brothers and sisters of today, were subjected to higher ultraviolet radiation from the sun because of the geographically closer location to the equator than Europe for example. Melanin is the natural pigment in our skin, which acts as a sunscreen to block out excessive and harmful ultraviolet radiation. A problem arises if too much melanin is present in skin tissue in areas where there is comparatively low ultraviolet radiation. Vitamin D cannot be properly synthesised, and therefore the absorption rate of calcium is restricted as a result. As Africans moved into Asia and then into Europe, the lower levels of ultraviolet radiation resulting from the geographical position, caused a reduction in melanisation of the skin through natural selection processes of evolution. Selective processes also moulded human physique and even skull size and head shape through differences in diet and adaptation requirements to different landscapes.

The genetic explanations of the spread of humanity through Asia is extremely interesting and detailed, making a clear distinction between the fact that genetics indicates molecular migration and movement and not necessarily cultural or racial migration. The impact of the climate is one, which is still dominant, and is most likely the driving force, which either pushed or pulled the human population into the regions it is historically known from. We were always going to be impacted by our environment, leading us to make decisions for survival. It is ironic to think that humans through technology have since conquered this barrier and it is now the environment, which is being manipulated by us, possibly to our future detriment.

I agree with the author’s assessment of academic rivalry and politics, which he terms as “academic civil wars” or “turf wars.” Using the example of the origins of modern humans into the Americas, he does not merely present the information as “fact,” but I feel that he gives the reader the neutral observer position to firstly present possible alternative solutions to whether modern humans migrated before or after the major ice-age into America, before allowing one’s own judgement on the academic processes involved in controversy. I feel that this is another reflection of the earlier suggestion of scientific propaganda and prejudice.

The message ringing clear in my mind after reading this book, on a purely objective front, is one of placement and clarity. Placement of who we are and how we got here, and clarity about our vulnerability, yet strengths as well. Evolution has taken the next step and has not stopped with us. We are constantly under evolutionary stressors, be them disease, overcrowding, and general competition. We have entered an evolutionary path of the mind, where the next path of eve could well see the human race exceeding its physical boundaries once again, though not through the graces of climate, but rather our own intelligence and ingenuity, possibly to other worlds. On the flip side though, could our thirst for development and power not lead us to our own extinction before our ultimate goal? What has happened to our natural innocence?

In general I enjoyed the book, however I have my reservations as indicated above. I recommend this book to anyone who is interested in their own heritage and history, even pre-history. For me the significance in this book does not lie in its historical documentation and link with genetics, but with a future message and a classic contrast with what we are doing to our environment now, compared to how we lived then.

David Vaughan
Senior aquarist, Quarantine
Two Oceans Aquarium
Cape Town, South Africa