Early in the morning of 19th February 2021 here in Perth, Australia, I attended a virtual seminar at Liverpool John Moores University to listen to a talk given by someone I had always regarded as one of my heroes… Richard Potts.

Potts studied the paleohabitats of Oligesaile, a key hominin site in the East African Rift Valley and found that rather than savannah habitats dominating the scene, there was an amazing cyclic shift from wet to dry to wet to dry and back, in ever increasing phases and frequencies. Periods of greatest change seemed to coincide with major steps in our evolution. He called this the “Variability Selection Hypothesis”.

When I read one of his key papers in 1998 it occurred to me that there was an elephant in the room that he had overlooked… water.

The key changes were to do with the amount of rainfall. In one period there’d be grassland, the next a swamp. Then it would get really arid for a few tens of thousands of years and then it would be a massive lake for a similar period.

The key changes were to do with the amount of rainfall. In one period there’d be grassland, the next a swamp. Then it would get really arid for a few tens of thousands of years and then it would be a massive lake for a similar period.

I made this point to him in a question after his lecture last night. I suggested that seasonally flooded gallery forest habitats was the perfect scenario to induce bipedal wading and the presence of lakes would encourage swimming and diving. I asked “why is the so-called ‘aquatic ape’ theory always ignored?”

The reaction to my question from some of the other attendees, that of dismay and ridicule, was illuminating. Robin Crompton shook his head in disgust and seemed to almost pull his hair out that someone could ask such a stupid question.

His reply was very disappointing. “Yes, I tend to ignore it” he said and suggested that hominins would have just walked around the lakes etc. and that it is as likely that hominins would have become adapted to living in higher terrain to avoid it. The faces of some of those in audience showed palpable joy and relief at this dismissal.

See below…

Potts did kind of apologise for being “too dismissive of it” but it continues to astound me how such as simple, plausible idea, backed up by so much evidence, continues to be ignored at best, or actively sneered at, at worst.

Of course there are “plenty of ways around water” just as there seems to be plenty of ways of ignoring a perfectly plausible hypothesis that has stared the field in the face for sixty years.

So, not so much a hero as I thought, then.

Algis Kuliukas
Perth
20th February 2021

Reference.

Potts, R. Environmental Hypotheses of Hominin Evolution. Yearbook of Physical Anthropology 41:93-136, (1998).