I’m sorry to report that Sir David Attenborough done screwed up. He is using his mellifluous voice and awesome reputation to promote the Wet Ape Theory. The show features all the usual suspects: recordings of Elaine Morgan insisting that her story is reasonable, Marc Verhaegen’s pseudoscientific hairsplitting, cartoon versions of evolution by Robert Ardrey and Desmond Morris, and that incessant nonsense of ignoring the whole organism and the existing evidence to argue that, well, this one little piece of our physiology could have evolved in the ocean, therefore we should claim that the whole beast was aquatic, because that is the only way they can now imagine it evolved.
The classic example is Alister Hardy’s initial hypothesis to explain why humans are hairless and have a layer of subcutaneous fat. What other animals have such a combination? Why, whales! They live in the ocean, and have lost most of their hair for better streamlining, and built up fat for insulation, therefore…humans lost their hair to better cut through the water, and evolved subcutaneous fat for heat retention. This is a bad hypothesis, because it ignores so much.
We don’t have any other streamlining adaptations, and are actually rather clumsy in the water.
Only aquatic mammals that live full time in the water show these adaptations; mammals that live part time in the water tend to have lots of hair.
Our “blubber” does a poor job of protecting us from that big heat sink, the ocean. We also lack the circulatory adaptations that make it useful in that function: countercurrent exchangers, arteriovenous anastomoses, that sort of thing.
Marine mammals have very little visceral fat; we’ve got loads of it. OK, I’ve got lots. Most of our fat is not distributed in a way to improve insulation.
And most annoyingly, the wet ape proponents simply pretend alternative explanations don’t exist. Hairlessness or reduced body hair, for instance, has evolved independently in several groups: cetaceans, naked mole rats, domesticated pigs, elephants, hippos, etc. So there are different strategies or environmental conditions that can lead to these features, and you can’t simply say all hairless mammals had to have gone through a dolphin-like evolutionary stage, because there are no other situations that can favor hairlessness.
But of course wet ape fanatics do — I’ve seen them seriously suggest that elephants had to have also gone through an aquatic phase.
Attenborough, I’m sorry to say, also takes this blinkered attitude. He closes episode 1 (there are two, I couldn’t bear to listen to the second) of his “waterside ape” series with what he proposes to be a “test” of the aquatic ape theory, which is no such thing. He claims to have new evidence: that there is a known feature of human infants which he predicts would be found in newborn cetaceans, and if confirmed, would both demonstrate the predictive power of the wet ape theory and provide an additional point of confirmation.
That feature is vernix, which is only known in humans. Vernix is the slimy, greasy coat that covers newborn humans, which he wants to claim is an aquatic adaptation, and therefore should be also found in other aquatic mammals. He is able to triumphantly announce that something similar has recently been reported in cetaceans.
But, again, the connection to an aquatic life has not been demonstrated. I don’t even see how vernix helps a mammal thrive in the water; it’s a fetal feature that is lost with the first bath, or is shed within a few days of birth. Vernix has many hypothesized functions for humans:
Vernix caseosa is a white, creamy, naturally occurring biofilm covering the skin of the fetus during the last trimester of pregnancy. Vernix coating on the neonatal skin protects the newborn skin and facilitates extra-uterine adaptation of skin in the first postnatal week if not washed away after birth. It consists of water-containing corneocytes embedded in a lipid matrix. The strategic location of the vernix on the fetal skin surface suggests participation in multiple overlapping functions required at birth, such as barrier to water loss, temperature regulation [the paper later shows a lack of support for this function –pzm], and innate immunity. Vernix seems to perform various integral roles during transition of the fetus from intra-uterine to extra-uterine life. It has also found various interesting diagnostic and prognostic implications in this arena. Thus, it continues to be an intriguing topic of interest among the medical fraternity to understand its detailed biology and function in the fetus and also to put its naturally endowed characteristics to use in the adult population.
Most of those multiple overlapping functions have nothing to do with adaptations for swimming — they are important for a mammal with no insulating layer of hair that is basically born prematurely with relatively few defenses. It is a logical error to imply that sharing a feature with many functions, like vernix, means that two species had to have had a similar ecological history. It makes no sense at all. I am very disappointed that David Attenborough has fallen for such crank nonsense.
I am not being peculiarly fussy, either. Very few people in the evolutionary/anthropological community think the Aquatic Ape is a credible hypothesis. Jim Moore has a very thorough compendium of rebuttals to the hodge-podge of contradictory details that make up the Aquatic Ape Theory; it’s a constant struggle to combat proponents who vomit up all kinds of odd scientific factlets that they claim are supportive of their cherished, much-loved, stupid theory. John Hawks explains why the AAT is pseudoscience. The Guardian has already posted a rejection of Attenborough’s “wishful thinking”. Alice Roberts quickly wrote an excellent response to Attenborough.
The original idea, and certainly Elaine Morgan’s elaboration of it, became an umbrella hypothesis or a “Theory of Everything”; both far too extravagant and too simple an explanation. It attempts to provide a single rationale for a huge range of adaptations – which we know arose at different times in the course of human evolution. Traits such as habitual bipedalism, big brains and language didn’t all appear at once – instead, their emergence is spread over millions of years. It’s nonsense to lump them all together as if they require a single explanation.
Despite the evidence stacked up against the theory, it is strangely tenacious. It has become very elastic, and its proponents will seize hold of any mentions of water, fish or shellfish in human evolution, and any archaeological sites found near coasts, rivers and lakes as supporting evidence. But we must always build our hypotheses on, and test them against, the hard evidence: the fossils, comparative anatomy and physiology, and genetics. In that test, the aquatic ape has failed – again and again.
It is a great shame the BBC recently indulged this implausible theory as it distracts from the emerging story of human evolution that is both more complex and more interesting. Because at the end of the day science is about evidence, not wishful thinking.
Unfortunately, I’m sure this bad idea will emerge again and again. There’s something appealing to the human psyche about one simple explanation of everything, even if that explanation is completely wrong.