What do you think why the Aquatic Theory isn't accepted by science?

Because there is no evidence at all to support it beyond a few incredibly feeble attempts to draw conclusions from a few coincidences, and because there are massive PILES of evidence that allow us to clearly and conclusively trace our lineage through land-based life forms, none of which the AAH even bothers to attempt to address, let alone explain.

In science, evidence is all that matters.

The Aquatic Ape Hypothesis (AAH) is not a theory. A theory is a hypothesis that has been well tested and withstood falsification.

One way to test a hypothesis is to make predictions and then test those predictions. The AAH argues that humans evolved bipedalism and a hairless body because our ancestor were wading for food, and were swimming a lot. The prediction therefore is that swimming is very likely to result in bipedalism and hairlessness. While it is true that manatees, dugongs, whales and dolphins have lost their hair when they adapted to an aquatic lifestyle, there are many animals that have not lost their hair nor have they become bipedal even though they spend a lot of time swimming and/or wading. For example, otters, raccoons, beavers, muskrats, and capybaras spend a lot of time wading or swimming and yet none of them is either bipedal or hairless. In contrast, many dinosaurs were bipedal, and yet there is little evidence that most of them were spending a lot of time swimming. Further, there are also mammals that are largely hairless but they are not very aquatic. Although elephants spend a lot of time daily in the water, they do it to cool off, and a hairless body allows them to stay cool on land, since they don't need insulation. Other large mammals living in warm regions are also largely hairless. For example, the rhino, giraffe and zebra has very short fur because they don't need insulation. The naked mole rat is hairless, but it is not aquatic. Hairlessness therefore can evolve among terrestrial mammals that do not swim regularly. Therefore this particular prediction has largely been falsified.

Another prediction is that swimming leads to an increase of subcutaneous fat. Although it is true that whales, dolphins and seals have a substantial layer of subcutaneous fat, other mammals that swim regularly do not. For example, sea otters rely on their dense fur for insulation. Besides, subcutaneous fat in aquatic mammals is used for insulation, not for swimming. Therefore it can also evolve in animals that live in cold climates. In fact subcutaneous fat is an adaption for cold weather in some populations. It is not universal among all human populations. Humans evolved originally in Africa, and most Africans do not have a thick layer of subcutaneous fat. We can see this in bra sizes. African women have an average of a B cup but Scandinavian and Russian women have much larger breasts, averaging a D cup, due to larger amounts of subcutaneous fat. Therefore once again a prediction made by the AAH has been falsified.

Scientists only elevate a hypothesis to theory status if it has withstood falsification, and they regard theories as scientific fact. Evolutionary theory has withstood repeated attempts to falsify it. It is widely accepted as fact because it has never been falsified. The AAH OTOH has been falsified because alternative explanations for hairlessness and bipedalism are available and they are more likely. For example, many animals stand on two legs to look out for danger, and since the savanna is so dangerous, bipedalism allows our ancestors to watch out for danger full time. Further, bipedalism evolved among the earliest hominids, such as Ardipithecus and Australopithecus, but there is no evidence that they spent a lot of time wading or swimming. Proponents of the AAH claim that Homo erectus and Neanderhals spent a lot of time swimming because their ears showed evidence for narrowing of the ear canal due to bony growths protruding into the ear that are caused by regular exposure to cold water, but bipedalism had evolved long before these 2 species did. If Ardipithecus shows evidence of a narrowing of the ear canal, then the AAH would be more plausible. That means bipedalism evolved before any hominid was spending a lot of time in water. Perhaps bipedalism made it easier for our ancestor to swim because apes like the gorilla and chimpanzee cannot swim. So, instead of swimming leading to the evolution of bipedalism, the evolution of bipedalism as an adaptation to living in the hot dry and dangerous savanna may have enabled swimming instead. The fact that AAH has been falsified is why it is not widely accepted by scientists. It is only accepted by those who have blind faith in this hypothesis and they treat it more like a religious dogma than a scientific hypothesis, because they ignore opposing evidence and insist that they are right.

Lack of evidence. If they ever found something that wasn't just-so or circumstantial, I don't see why science wouldn't accept it. The theory had some champions at first, but it fizzled.

Why don't you ask about it in the science categories?

billions of years ago your anscestors lived in the sea. so technically its true

Another 60s crazy New Agey piece of nonsense. Every serious paleoanthropologist has flatly rejected it.

Probably because it doesn't deserve acceptance. I'm not sure since I never heard of it nor will I make an effort to find out what it is.

Simplistically, criticism arises because "it's always a problem identifying features [such as body fat and hairlessness] that humans have now and inferring that they must have had some adaptive value in the past." Also "it's notoriously hard to infer habits [such as swimming] from anatomical structures".

The research continues.