Behavior In Water | Center for Academic Research and Training in Anthropogeny (CARTA) (2023)

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Most mammals are able to swim instinctively without training; a notable exception being the great apes. Humans are clearly able to become proficient swimmers with training; other great apes, however, have not been documented as swimmers beyond anecdotal reports. Chimpanzees, for example, are claimed to enjoy playing in water but not to swim. The unwillingness to swim is strong enough that it presumably played a role in the speciation of common chimpanzees and bonobos, which are geographically separated by the Congo River. Notably, this finding does not extend to all primates, as some monkey species, such as crab-eating macaques and proboscis monkeys, have been observed swimming underwater.

A difference in affinity for water between humans and the other great apes may result simply from behavioral differences between species. For example, most apes may have an instinctive fear of predators or drowning. Interestingly, fear of water is one of the most common phobias in humans; along with similar phobias such as those of spiders and snakes, it has been proposed to be an “evolutionarily relevant” phobia that could confer a selective advantage.

This potential difference could also result, however, from physiological differences. Accordingly, a number of features of modern human physiology have been proposed as means by which humans, but not our closest relatives, are able to swim. These include: an infant swimming reflex, a diving reflex, voluntary breath-holding, and buoyancy provided by increased adipose tissue. However, these examples do not hold up well under scrutiny.

The infant swimming reflex describes “rhythmical, coordinated movements, with inhibition of breathing” seen in human infants placed prone in water until approximately 4-6 months of age. However, this reflex can be seen in other neonatal mammals, including apes, and is therefore not human-specific.

In the diving reflex, contact of the face with cold water causes bradycardia (slow heart rate), apnea (breath-holding), and peripheral vasoconstriction. This allows an animal to conserve oxygen while swimming underwater. Again, the diving reflex can be found in all mammals.

Voluntary breath-holding, found in humans,
has been reported to exist in other mammals including apes. The ability to study this is significantly impaired by the methodological limitation of inducing a non-human animal to hold its breath. Further, the relevance of this feature to swimming is unclear given that reflex apnea is a feature of the diving response. Human bipedalism, in which the movement of the diaphragm has less postural constraint, may be at least partially responsible for any true differences in breath control between humans and other apes.

Lastly, it has been argued that swimming requires a degree of buoyancy provided by a high body fat to muscle ratio. Humans seem to have an exceptionally high degree of adipose tissue in comparison with other primates, although this finding is clearly complicated by the rates of overweight and obesity in modern human populations.

These and a large range of other features of human physiology have been suggested by proponents of the “Aquatic Ape Hypothesis” as indications that humans descended from an aquatic ancestor. This hypothesis has been largely discredited.

Aquatic foods such as crocodiles, turtles, and fish have been implicated in the hominin diet as far back as 2 million years ago in Kenya. Essential fatty acids are high in fish; in particular, the omega-3 fatty acid docosahexaenoic acid (DHA) is much higher in fish than other dietary sources. These fatty acids are high in brain tissue and important to brain function. It has therefore been proposed that a near-water habitat and the harvesting of aquatic foods were important features of early Homo.

(Video) CARTA: Anthropogeny in Medicine and Health - Cynthia Beall: Adaptations to High Altitude

Timing of appearance of the difference in the Hominin Lineage as a defined date or a lineage separation event. The point in time associated with lineage separation events may change in the future as the scientific community agrees upon better time estimates. Lineage separation events are defined in 2017 as:

  • the Last Common Ancestor (LCA) of humans and old world monkeys was 25,000 - 30,000 thousand (25 - 30 million) years ago
  • the Last Common Ancestor (LCA) of humans and chimpanzees was 6,000 - 8,000 thousand (6 - 8 million) years ago
  • the emergence of the genus Homo was 2,000 thousand (2 million) years ago
  • the Last Common Ancestor (LCA) of humans and neanderthals was 500 thousand years ago
  • the common ancestor of modern humans was 100 - 300 thousand years ago

Possible Appearance:

6,000 thousand years ago

(Video) CARTA: The Role of Hunting in Anthropogeny: Questions and Answers

Probable Appearance:

2,000 thousand years ago

Definite Appearance:

100 thousand years ago

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Voluntary Control of Breathing Likely
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  1. Early hominin diet included diverse terrestrial and aquatic animals 1.95 Ma in East Turkana, Kenya, Braun, David R., Harris John W. K., Levin Naomi E., McCoy Jack T., Herries Andy I. R., Bamford Marion K., Bishop Laura C., Richmond Brian G., and Kibunjia Mzalendo , Proceedings of the National Academy of Sciences, Volume 107, p.10002-10007, (2010)

  2. Adipose tissue in human infancy and childhood: an evolutionary perspective., Kuzawa, C W. , Am J Phys Anthropol, 1998, Volume Suppl 27, p.177-209, (1998)

  3. Rift Valley lake fish and shellfish provided brain-specific nutrition for early Homo., Broadhurst, C L., Cunnane S C., and Crawford M A. , Br J Nutr, 1998 Jan, Volume 79, Issue 1, p.3-21, (1998)

  4. Mode of onset in evolutionary-relevant and evolutionary-neutral phobias: evidence from a clinical sample., Menzies, R G., and Harris L M. , Depress Anxiety, 1997, Volume 5, Issue 3, p.134-6, (1997)

  5. Umbrella hypotheses and parsimony in human evolution: a critique of the Aquatic Ape Hypothesis., Langdon, J H. , J Hum Evol, 1997 Oct, Volume 33, Issue 4, p.479-94, (1997)

    (Video) CARTA:Todd Preuss-Uniquely-Human Features of the Brain: Enhanced Cerebral Metabolism and Plasticity

  6. Swimming Behavior of the Human Infant, McGraw, M.B. , The Journal of Pediatrics, Volume 15, p.485-490, (1939)


Why can't great apes swim? ›

The tree-dwelling ancestors of apes had less opportunity to move on the ground. They thus developed alternative strategies to cross small rivers, wading in an upright position or using natural bridges. They lost the instinct to swim. Humans, who are closely related to the apes, also do not swim instinctively.

Can chimpanzees and bonobos mate? ›

But, as our study reveals, there is evidence of ancient genetic mixing across species boundaries. We now know that hundreds of thousands of years ago, chimpanzees and bonobos were able to mate and produce offspring, leaving a genetic mark on the animals that live in the wild today.

Can apes walk on two legs? ›

Apes on the ground usually travel quadrupedally. They make only occasional use of bipedalism, often in the context of display. Bipedal walking is the normal slow gait of birds, and running is the fast terrestrial gait of many of them.

What mammal can't swim? ›

Most mammals are capable of swimming. But there are some animals that are incapable of swimming. Giraffe is one of the animals that cannot swim and it is because of their extreme anatomy – such as their long necks and legs, which would make swimming almost impossible.

Why are humans not natural swimmers? ›

The human body is not really made for swimming. It is made for walking and running. Our upright gait on two legs sets us apart from other mammals—the ones our ancestors were chasing on foot. Our unusual anatomy actually makes swimming harder for us than it is for animals that go about on four legs.

Can apes be taught to swim? ›

These primates – Cooper the chimp and Suryia the orangutan – were raised and cared for by humans and have learned to swim and to dive.

What is labial rubbing of the bonobo? ›

Of the two species, bonobos are the only one to exhibit a unique socio-sexual behavior called genital-genital rubbing or “gg” rubbing. This behavior is thought to ease social tension and promote social bonding among group members.

Can human sperm fertilize chimpanzee? ›

Humans and chimps have DNA that is 95 percent similar, and 99 percent of our DNA coding sequences are the same as well. However, humans have 23 pairs of chromosomes in our DNA, while chimps only have 22. The difference makes bearing healthy young difficult, and the offspring would be infertile.

Could a gorilla and a human have a baby? ›

Although it's hard to say anything with absolute certainty, human DNA is so different to even our closest relatives that interbreeding is probably impossible. Despite this, Gallup believes that it is possible to crossbreed humans with great apes, including gorillas and orangutans.

Are humans still evolving? ›

Broadly speaking, evolution simply means the gradual change in the genetics of a population over time. From that standpoint, human beings are constantly evolving and will continue to do so long as we continue to successfully reproduce.

Did humans evolve from monkeys? ›

How are humans and monkeys related? Humans and monkeys are both primates. But humans are not descended from monkeys or any other primate living today. We do share a common ape ancestor with chimpanzees.

Who was the first human on earth? ›

Homo sapiens, the first modern humans, evolved from their early hominid predecessors between 200,000 and 300,000 years ago. They developed a capacity for language about 50,000 years ago. The first modern humans began moving outside of Africa starting about 70,000-100,000 years ago.

What animal can't stop swimming? ›

Other Marine Animals that Don't Stop Swimming

Sharks are just like the manta rays; they need to keep moving forward at all times. One exception is the whitetip reef shark, which can lay down like a stingray and push water over its gills. Tuna is another type of fish that doesn't stop swimming throughout its lifespan.

Which is the only mammal that cant jump? ›

Elephants can run up to 25 miles per hour. However, they remain the only mammal on earth that can't jump. They always keep one leg on the ground - even when running.

Which animal Cannot jump? ›

Elephants cannot jump, but are they the only mammal that cannot jump? Rhinos, hippos, and sloths are often mentioned as other examples of mammals that aren't able to jump, though rhinos and hippos can lift all four feet off the ground while running.

Why don't gorillas like water? ›

Like the other apes and humans, gorillas cannot swim naturally, therefore they avoid large bodies of water and rivers. However, in zoos and sometimes even in the wild, young and adult animals like to play with water.

Do great apes have Down syndrome? ›

Trisomy 22 is diagnosed when the cells of apes such as chimpanzees, gorillas or orangutans contain a third copy of chromosome 22. The first confirmed case of a chimpanzee with trisomy 22 was documented in 1969. The chimpanzee described nearly five decades ago died before its second birthday.

Why gorillas can't swim? ›

Gorillas, like the other great apes, are not born with an instinctual ability to swim. Large bodies and a dense bone structure would make it difficult, even if they did attempt it. In their daily lives, gorillas rarely encounter deep water and have evolved to survive without swimming.

Is there any truth to the aquatic ape theory? ›

The idea was purely hypothetical. No fossil evidence pointed to such an aquatic ape. But Hardy saw the absence of fossil evidence as an opportunity. At the time, there seemed to be a long space of time between known Miocene apes like Proconsul and the earliest bipedal hominin, Australopithecus africanus.


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3. CARTA: Cellular and Molecular Explorations of Anthropogeny - Welcome and Introduction
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4. James Rilling - Human Brain Specializations Related to Language
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5. CARTA: The Genetics of Humanness: Ajiit Varki - Human-Specific Changes in Siglec Genes
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6. CARTA: Human Origins: Autism Spectrum Disorders - Simon Baron-Cohen: The Fetal Androgen Theory
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