Was there a Garden of Eden?

The first chapters of the Bible describe our human origins as deriving from a single set of parents in a place called the Garden of Eden. That mythical account is not far removed from what anthropologists and geneticists are now telling us – though we are still far from consensus on the matter.

The name Homo sapiens (Latin for “wise man”) was coined in the early 18th century by a Swedish botanist, Linnaeus, who recognised that all humans were part of one species. What does that mean? Since the mid-20th century a species has been defined as an interbreeding (or potentially interbreeding) group of organisms. If it’s possible to produce offspring together, you must be of the same species.

But Linnaeus also believed that our Homo sapiens species was divided into distinct sub-species or races. And when evolutionary theory became popular in the 19th century, it was widely believed that these races – identified as African, Native American, East Asian, and European – had evolved at different times and in different places. The theory sat comfortably with Europeans. It meant that they were the most recent and therefore the most advanced race to evolve, while the others, especially the dark-skinned Africans and Native Americans, were downright primitive by comparison. It found further support when the philosopher Herbert Spencer coined the phrase “survival of the fittest” – (a phrase that was never used by Darwin) – and used it to justify the social divisions inherent in late-19th century Britain. So now there was scientific justification for believing not only that the Aryan race was superior to all others, but that people who occupied the top strata of society deserved to be there since they must be more “fit” than the mere peasants.

By the end of the 19th century this widespread belief had given rise to the eugenics movement – (“eugenics” means “good birth”) – which in 1907 gave birth in Britain to the Eugenics Education Society, the stated objective of which was to improve the gene pool of humanity through the selective breeding of “fit” individuals. Supported by the best scientific evidence of the time, the elite loved it. By the 1910s and 1920s it was being used in the U.S. as justification for the forced sterilization of people believed to be mentally subnormal. And from there it was only a short step to the Nazi death camps and the systematic extermination of Jews, gypsies, homosexuals, and other supposedly inferior groups.

In the 1960s, we were still finding scientific justification for such thinking. The American anthropologist Carleton Coon advanced the idea, very like that of Linnaeus 250 years earlier but now known as the “multi-regionalism hypothesis”, that there are five distinct human subspecies that evolved at different times into their present form from ancestral hominids. The basic idea is that ancient hominid species migrated out of Africa over the past two millions years, established themselves in East Asia very early on, and then evolved in situ into modern-day humans – creating the different races in the process. Again, it was the African “Congoids” that appeared first and have remained trapped ever since in an evolutionary dead-end.  And of course the dominance of the more recently evolved Europeans is a natural consequence of their genetic superiority.

Since then the debate has continued to rage. In 1987, an analysis of mitochondrial DNA declared that all modern humans descended from one African population within the last 140,000 years. It was a serious blow to multi-regionalism. But by 1992, that study had been largely discredited. Then, in late 2000, a Swedish study of mitochondrial DNA again seemed to demonstrate that all modern humans emerged from Africa within the past 100,000 years and came from a breeding stock of no more than 10,000 individuals.

It began to look like the multi-regionalism hypothesis was dead. Indeed, most scientists who have studied the matter now agree that all modern humans evolved in Africa within the past 200,000 years. Their direct ancestor was probably the species Homo heidelbergensis that appeared on the scene in Africa some 500,000 years ago and then migrated into Europe. Those that went to Europe later evolved into Neanderthal Man, while those that remained in Africa evolved into modern Homo sapiens. Geneticist Spencer Wells claims to have identified our ancestry even more specifically as Mitochondrial Eve – the African great-great- .... grandmother of us all who lived about 150,000 years ago.

Where did Mitochondrial Eve live? Where, in other words, was the Garden of Eden where our first parents originated? We don’t know specifically, but it was almost certainly somewhere in the Great Rift Valley. A recent genetic survey suggests that a region on the coast of southwest Africa near the Kalahari Desert, at the southern terminus of the Rift Valley, may be our place of origin. It is now homeland to the Bushmen or San people who represent a direct link back to our earliest ancestors. But at that time, the San occupied a much larger area that stretched from southern Africa up the east coast as far as present-day Ethiopia – so the Garden of Eden could have been anywhere within that Valley.

How did this one family of humanity develop distinctive physical traits among different geographic groups – the traits that we used to think represented separate “races”? Some 60,000 years ago, Homo sapiens began to leave Africa and spread across the globe to colonise the entire planet. The physical traits that distinguish modern geographic groups subsequently developed as an adaptation to local environmental conditions. So skin colour varies with the intensity of sunlight in a given region to ensure the necessary absorption of Vitamin D. It has nothing to do with racial identity. We really are one family.

Or are we? In actual fact, the multi-regionalism hypothesis is far from dead. Where, for instance, did the aboriginal people of Australia come from? Spencer Wells and others argue that they migrated there from Africa. But there’s a problem. Although modern humans are thought not to have left Africa before 60,000 years ago, human remains dating to 62,000 years ago have been found at what was once Lake Mungo in the interior of Australia. Even if our dating is off by a bit, migrants from Africa would certainly have had to hustle in order to arrive first in Indonesia, then build ships and navigate a few hundred kilometres of open sea, and finally move more than 2000 kilometres inland from the northern Australian coast to Lake Mungo.

More than this, as recently as 2001, Alan Thorne and his colleagues at the Australian National University reported that mitochondrial DNA from the oldest of the Mungo residents was genetically distinct. It is no longer found in living humans, as it should be if he was descended from the people who left Africa. And then Rosalind Harding, a population geneticist at Oxford, found two genetic variants that are common among Asians and the indigenous people of Australia, but hardly exist in Africa. These variant genes, she is certain, arose more than 200,000 years ago, not in Africa but in East Asia – long before Homo sapiens reached the region. Where then did the aboriginal people of Australia come from? Could it be, as Alan Thorne proposes, that human evolution has been continuous and that different strains of Homo sapiens evolved from Homo erectus – who was already in Indonesia, and only a sea voyage away from Australia, long before the Africans even began their migration eastward?

I, for one, would still like to believe that we are all one family that originated in an updated version of the Garden of Eden somewhere in Africa. But the supporting evidence is not nearly as clear as we might like to think. With any kind of luck, a revival of the multi-regionalism hypothesis will not also revive the racism that we are having such difficulty leaving behind. The moral of the story seems to be this: Be careful lest you too quickly embrace supposedly “hard evidence” to support your own personal prejudices and predilections.