Thursday, June 16, 2011

Modern Humans Extinction-Proof?

Darren Curnoe is in the news again. Last year, he coined a new species at the boundary of late Australopithecus/early Homo, named Homo gautengensis, which made such a large splash in the community that there have since been ZERO articles on it from other researchers. It is classified as Homo habilis by everyone else. I asked my advisor about Homo gautengensis and he replied “Homo what?”

Curnoe is now arguing that humans are extinction-proof. Gavin Allen of the Mail Online writes:
There were around 100,000 hunter-gatherers in the Ice Age and now the worldwide population stands at approximately seven billion.

Curnoe says: ‘Seen in its broadest context, the history of life on Earth soberly demonstrates that the vast majority of organisms that ever lived, perhaps 99 per cent of them, no longer do’ wrote Curnoe.

‘It also shows that mammal species normally last 1-2 million years before extinction inevitably bumps them off.

‘Yet, unlike most mammals, including our dozens of extinct hominin cousins, we have escaped the vulnerabilities of a small and massively fluctuating population.

‘The simple, but profound act, of growing our own food delivered us the food security that ensured most of our children survived and our population grew.

‘In effect, farming gave our species level assurance that the biological isn’t always inevitable. The odds have shifted to such a degree that we may now be, with or without climate change, extinction-proof.’
Curnoe is certainly right that the advent of farming and agriculture significantly changed the environment and led to humans being able to control the landscape to a much greater degree but I would argue that as important was a change that took place much earlier in our history: the loss of estrus.

At some point in our past, humans acquired the ability to be continously sexed. We can procreate any time we want. This is important, given our reproductive strategy. Primates fall into the class of organisms that are “k-selected.” We usually have only one offspring at a time and we invest much energy and time in getting that child to reproductive age. The counter to this is an r-selected animal like the sea turtle, which lays over a hundred eggs in the hopes that some of them survive into adulthood. By the time they hatch, the mother turtle is long gone.

While it is certainly true that human babies born in winter had less of a chance of survival before the advent of modern technology and heating, to be able to mate at any opportunity vastly expands the ability of the population to increase quickly. Gorillas, on the other hand, can only procreate once every three years.

There have been extinctions in human history but there has also been species evolution resulting in the appearance of modern humans between 150 and 170 thousand years ago. Further, the technological advances with which we have surrounded ourselves were likely not an outgrowth of increasing intelligence but rather an increasing population, driven by the loss of estrus. Without some high level of food security, k-selected populations do not increase that fast.

It could, therefore, be equally argued that agriculture was an outgrowth of the need to feed large populations, and that it might not have been agriculture that made us "extinction-proof" but simply a large enough increase in the population to the point where it made us almost impossible to kill off.

P.S. As to whether or not we are extinction proof, one really large meteorite and we're toast.


  1. I agree with you. To argue that humans are extinction proof shows a lack of perspective (our species has only been around 200K years) or a lack of imagination (there are many scenarios that could have the world-wide impact needed to wipe out all humans).

  2. The argument just struck me as being a bit “ubermensch” in tone.

  3. Re: "…and we're toast," I think that's why we can't afford a dwindling space program. Not sure how long it would take for the earth too cool down to livable temps after such an event, but at least temporary colonization of Mars could buy us some time until then. Or a permanent convoy.