One of the things that has always made me uneasy about the standard savannah story of human evolution is not so much that it is wrong in detail, but that it is wrong in temperament. It is far too heroic. Our ancestors stride confidently out of the forest, shed their fur, stand upright to scan the horizon, invent fire just in time, and somehow endure a long period of anatomical half-finishedness without dying of thirst, heat, infection or sheer inconvenience. Evolution, however, is not heroic. It is cautious, opportunistic and relentlessly focused on the short term. If something does not work on an ordinary Tuesday, it does not get refined over the next hundred thousand years. It simply gets selected out.
The idea of The Inundated Ape starts from a less dramatic but more plausible premise. Instead of imagining a forest ape boldly choosing a new lifestyle, imagine a forest ape whose environment is gradually, repeatedly and inconveniently altered by water. Floodplains expand. Forest floors become seasonally waterlogged. Rivers change course. Lake margins appear where solid ground used to be. The ape is not aspiring to anything. It is being inconvenienced. It is, quite literally, inundated.
What first pushed me in this direction had nothing to do with bipedalism, tools or language, and everything to do with three very mundane features of the modern human body. The first is head hair and beards. They grow continuously and, if one wants them to look even vaguely decent, require not just cutting but regular washing and something very like conditioner. As somebody with daughters with long hair, I am painfully aware that without frequent soaking, detangling and lubrication, it rapidly becomes a matted problem. What makes this harder to dismiss is that hair reduction is not a recent quirk layered on top of an otherwise hairy primate body. The split between human head lice and pubic lice suggests that humans already had distinct hair zones several million years ago, which in turn implies that substantial hair loss must be ancient rather than a late, cosmetic development. Whatever made reduced body hair viable must therefore have been in place very early. The second is toenails, which also grow without obvious limit and become genuinely disabling if they are not worn down. The third is defecation. Humans have large, rounded buttocks, smooth skin and an upright posture that presses the cheeks together. This is a remarkably poor design if one does not wipe or wash.
These are not aesthetic complaints. They are daily survival issues. And what is striking is how neatly they are all solved by frequent contact with water. Regular wetting and drying weakens hair shafts and encourages breakage at the ends. Water acts as a natural conditioner, reducing tangling and allowing fingers to do much of the work that combs would later take over. Sand, silt, mud and uneven ground wear down nails without conscious effort. And access to shallow water turns defecation from a medical hazard into a trivial interruption. One rinses, one moves on. No tools, no privacy, no ideology required.
Diet sharpens this picture rather than blurring it. The offensiveness of faeces is driven largely by protein putrefaction. Herbivore dung is bulky but comparatively inoffensive; carnivore dung is small, sticky and biologically aggressive. An omnivore becomes smellier the more meat it eats. A largely plant-based diet, supplemented by low-level animal protein, dramatically reduces the hygienic burden of defecation, especially for a hair-reduced, upright animal. Such a creature is perfectly viable if washing is routine. The same creature living far from water and eating meat daily is an infection waiting to happen. Evolution notices that sort of thing quickly.
Seen from this angle, bipedalism also loses much of its mystique. Standing upright on an open plain is dangerous. Standing upright in shallow water is immediately useful. It keeps the head dry, frees the hands, allows one to see over reeds, and makes carrying infants or food straightforward. Wading does not require heroic reinterpretations of anatomy. It merely requires an ape whose familiar forest floor has become intermittently submerged.
At some point, however, wading would no longer have been enough. Shallow water leads naturally to deeper water, and deeper water opens up new food sources. Freshwater mussels are an obvious example: stationary, protein-rich and available in large numbers to anyone who can dive briefly and feel around with their hands. Here, swimming, including underwater swimming, becomes useful rather than optional, and breath control ceases to be an incidental side effect of posture and becomes something that matters in its own right. One does not need to imagine a fully aquatic phase to take this seriously. Occasional diving for food is enough to reward individuals who can control inhalation and exhalation voluntarily, who can time their breaths, and who can stay calm underwater.
This is also where vocalisation begins to look interesting. As a linguist, I find the claim that breath control must have evolved for language deeply unconvincing. Humans are extraordinarily good at turning whatever channel is available into language. When sound is constrained, we sign. When articulation is limited, we whistle. Language is cognitive first and opportunistic second. Speech is simply the loudest and most flexible option once the machinery exists.
What does require explanation is why we have so much vocal control in the first place. Human speech uses only a fraction of our available pitch, rhythm and timing capacity. The surplus is overwhelmingly musical and social. We sing, chant, soothe infants, coordinate groups and vocalise for reasons that have nothing to do with propositional content. Song and rhythmic vocal play are far more plausible early uses of fine breath control than fully fledged language. They tolerate imprecision, work in low visibility, scale easily to groups and bind individuals emotionally. It is not difficult to imagine proto-humans sitting on branches over a lake, eating, grooming and singing, their voices carrying across the water long before anything we would recognise as language appears.
The food story fits naturally into this picture of gradual inundation. Aquatic plants and mussels provide early animal protein without the dangers of hunting. Scavenging on the savannah comes next, particularly bone marrow from carcasses killed by other predators, which offers a high-energy reward with relatively low risk. Only later does endurance hunting enter the picture, initially less as a means of killing large prey outright than as a way of reaching carcasses early and defending them with numbers, stones and persistence. Stone tools, at this stage, are as much about keeping other predators away as they are about processing meat.
A simple evolutionary control case helps keep all of this grounded. We already know what happens when a primate lineage leaves dense forest and adapts to open, seasonal terrain over long periods. We get baboons: quadrupedal, hairy, panting rather than sweating, behaviourally conservative and extremely successful. This is the default primate solution to plains life. If humans had truly lived full-time on the savannah for millions of years without technological scaffolding, this is roughly what we should expect them to look like. That we do not look like this is not a mystery to be explained away. It is evidence that the savannah was not our primary home.
A more plausible picture is that early humans used the savannah long before they lived on it. They made forays to forage, scavenge and eventually hunt, but they returned again and again to water to drink, wash, socialise and sleep. Permanent residence on dry plains requires containers for water, reliable fire, planning horizons beyond the day, and cultural norms around cleanliness. None of these appear automatically with bipedalism. Until they are in place, the savannah is somewhere you visit, not somewhere you belong.
This perspective invites a small but telling behavioural thought experiment. Animals tend to be comfortable in the environments they are adapted to. Not in any sentimental sense, but in the practical one that their bodies relax there. They rest easily, thermoregulate without fuss, and do not need constant behavioural workarounds. Baboons do not seek beaches. Gorillas do not holiday by lakes. A primate shaped by the savannah should, by now, find the savannah quietly agreeable.
Humans do not. Even with clothing, sunscreen, bottled water, vehicles and air-conditioned buildings, we do not choose open plains as places to linger. We cross them. We admire them briefly. We run across them for exercise, and then we leave. When we are free to choose where to stop doing things altogether, where to sit for hours with no purpose beyond existing, we choose water. Beaches, riverbanks, lakesides, swimming pools. We recreate the same arrangement wherever we go: a body of water, somewhere to sit beside it, and the option to immerse ourselves repeatedly. Children, in particular, will spend hours moving in and out of water for no instrumental reason at all.
If humans had evolved almost exclusively on dry plains, this would be a curious outcome. One would expect some deep residual ease there, some bodily sense that this is where things make sense without constant management. Instead, we behave like animals whose relationship with open, arid ground has always been conditional. We go there to get things. We return to water to rest.
Seen in this light, The Inundated Ape is not an aquatic fantasy, but a conservative reading of anatomy, behaviour and common sense. A forest ape whose world became wetter, patchier and less predictable was forced to cope with incomplete solutions. Hair reduction worked because washing was easy. Sweating worked because rehydration was constant. Upright posture worked because wading came before striding. Breath control emerged because swimming, social sound and posture all leaned in the same direction. Later still, the ape was inundated again, this time by behaviour and culture: fire, tools, meat, language, social complexity.
What emerged was not a specialist, but a creature unusually good at absorbing change without falling apart. We did not stride heroically out of the forest and discover that the savannah was our destiny. We were inundated, again and again, and learned to cope. And in the process, we became adaptable enough to live almost anywhere, while never quite forgetting where our bodies still feel most at ease.