Aquatic Ape Human Ancestor Theory

Aquatic Ape Theory - What is it?

A Brief Summary of AAT - key arguments

A Brief History and Key Proponents of AAT

When / Where / How?

Ape to Human Evolution Timeline

Alternative theories of human evolution

Wikipedia and the scientific community

... Anatomical Evidence
... Bipedalism
... Birth and babies
... Brain
... Breath control
... Descended larynx
... Diet
... Diseases
... Fat
... Fingers, toes and feet
... Furlessness
... Hair and baldness
... Human ailments
... Kidneys
... Language & Song
... Menopause
... Nose
... Olfactory sense
... Pachyostosis
... Paranasal Sinuses
... Platycephaly
... Reverse osmosis
... Sexual features
... Sleep (USWS)
... Surfer's ear
... Sweating
... Tears
... Underwater vision
... Viruses
... Waterside environments

. Homo Ancestors
... Trachillos bipedal hominids
... Homo erectus
... Homo neanderthalensis
... Sea Gypsies/ the Moken
... Homo sapiens - water afinity
... Coastal Migration
... Pan and Gorilla ancestry
... Semi-Aquatic Animals

. Testable Hypotheses
. Fossil evidence
. Genetic evidence
. Paleoecological evidence
. Retroviral marker in apes
. Acheulean handaxes

A call to scientists...

Recent News and Updates

Books and publications


Videos links



Homo erectus - shallow diver, litoral roamer

Homo erectus was probably the key to our aquatic history. It existed for close on two million years and in that time managed to travel further than any other ape species with the exception of ourselves. Their fossils have been found in riverside, lakeside or coastal locations in Africa, Asia, Europe and Oceania, often surrounded by fossilised remains of shellfish, turtle shells, crocodiles, catfish, stingrays, etc. [1]

Homo erectus was probably the first 'naked' homo, who subsisted mainly on aquatic foods and dived regularly in shallow waters, which were plentiful during the glacials when sea-levels reduced. They also travelled far around ancient coastlines and a group of them even made their way to the island of Flores (cf. Homo florenensiensis), 19km overseas, suggesting they were extraordinary swimmers (and/or possibly seafarers??). With their very heavy bones, they were also great divers and could probably reach depths and stay underwater for durations that exceed the capabilities of the best free-divers among Homo sapiens today.

Homo erectus possibly represents the first of our line with an increased cranial capacity in line with modern humans, as well as the invention/discovery/utilisation of: fire [3], hand-crafted tools [4], clothing [5], architechture [6], art [7], sculpture [8], language [9], healthcare [10], etc., which altogether constitute a form of culture. [10]

Venus of Tan-Tan and Venus of Berekhat Ram, possibly crafted by Homo erectus.

The Middle Pleistocene "Venus of Tan-Tan" (left) and "Venus of Berekhat Ram" (right) are postulated to been crafted by H. erectus to resemble a human form. They were mostly formed by natural weathering, but slightly modified to emphasize certain grooves to suggest hairline, limbs, and eyes. The former has traces of pigments on the front side, possibly indicating it was colored. Note the emphasis of 'fat' which indicates that Homo erectus may have been the first Homo species to develop subcutaneous body fat which aid buoyancy and thermoregulation in the water.

Sir Alister Hardy asked the question: "Was Man More Aquatic in the Past?" and the answer must surely be: yes. Homo sapiens generally survives today as a terrestrial species, with a strong affinity to water, residing predominantly near water, and with a large part of our diet still consisting of seafood. However, with the exception of a few distinct ethnic groups, human beings can no longer claim to be a semi-aquatic species.

But if we were more aquatic in the past, when was it and which species can claim that distinction? Of all the Homo ancestors, one stands out as being the most 'different' from the great apes, and has the most 'aquatic' features of all, including Homo sapiens.

"When the Dutch physician Eugène Dubois unearthed in eastern Java in the early 1890s the skull cap and the femur of what he first named Anthropopithecus and later Pithecanthropus erectus (now the type specimen for Homo erectus), he was struck by the extraordinarily massive cortical bone tissue, and he interpreted this as a sign of the primitiveness of these bones. Later researchers, such as Franz Weidenreich, thought the heavy bones suggested that H. erectus individuals were giant creatures. As more fossils were discovered, however, it became clear that, although not small, these individuals were no giants, but instead had relatively very compact and thick bones [2, 3], beyond the range of optimal strength/weight ratio. Different hypotheses have been put forward to explain this curious feature, but so far there has been no consensus." [1]

Comparative species with such heavy bones include the dugong and manatee, both shallow bottom feeders. Their bones provide useful balast so that they can remain under the surface for longer. The truth is that the increased density of the H.erectus skeleton would have left them wholly unsuited to running, or even prolonged terrestriality, as heavy skeletons are energetically expensive to move and their heavy, hyper-mineralized bones would have more easily fractured, a risk that rises with velocity. In other words, Homo erectus would probably have broken his legs if he had tried running across the savannah after prey. We can therefore assume that H.erectus likely made few sustained terrestrial forays. The summed evidence of bone gross morphology and micro-structure indicates that H.erectus were fully committed to an aquatic lifestyle, and bore marked adaptations for bottom-walking, paddling & undulatory swimming modes. [4]

See also: Homo erectus Litoralis, M. Verhaegen, London 2013 [pdf]


[1] Stephen Munro and Marc Verhaegen, Pachyosteosclerosis in Archaic Homo, Chapter 5. Was Man More Aquatic in the Past? Fifty Years after Alister Hardy, Waterside Hypotheses of Human Evolution, Bantham science publishers, 2011. p. 82
[2] Boaz T, Ciochon RL. Headstrong hominids. Nat Hist 2004; 113: 28-32.
[3] Boaz T, Ciochon RL. Dragon Bone Hill: An Ice-Age saga of Homo erectus. Oxford: Oxford University Press 2004.
[4] The postcranial skeleton of H.erectus after SI Madar 2007 J Paleontol 81:176


Homo erectusNot only does a waterside lifestyle fit well with the known nutritional needs of Homo sapiens, it can help explain many otherwise unexpected features of human anatomy, behavior and physiology.

Bramble and Lieberman [2] suggest that a shortened femoral neck could have been an adaptation to more efficient running, yet this feature first appears in Homo sapiens and is absent from earlier Homo species such as erectus. This implies that Homo erectus, with a relatively long and more horizontal femoral neck [3] was a less efficient runner than Homo sapiens. Other anatomical features point to the same conclusion, including the thicker, heavier cranial and post-cranial bones of Homo erectus and the less flexed cranial base [4]. With a generally thicker cortex and narrower medullar cavity, the limb bones of Homo erectus were dense and heavy compared to Homo sapiens and other primates, and the cranial bones were generally thicker as well [5-10]. The extra weight created would have been an unnecessary burden for an endurance runner [4]. Long-distance human runners are lightly built compared to sprinters, and cursorial mammals such as dogs and horses do not have thick, heavy bones.

The basicranium of Homo erectus is relatively flat compared to the very flexed condition seen in Homo sapiens [5, 11-13], and this is probably associated with a more elongated braincase and with a “peculiar poise of the head” [11]. The line of vision in Homo erectus, as a result of this peculiar poise, would have been somewhat more towards the sky than towards the horizon (or foreground) is the case in Homo sapiens. In a swimming/diving position, the less flexed basicranium of Homo erectus would mean the eyes were more naturally oriented in the direction the individual was moving (i.e., head first through the water). Although it remains to be seen how much time our ancestors may have once spent in the water, there is no doubt that the heavier bones of Homo erectus as well as the less flexed basicranium strongly contradict cursorialism [4].


[1] C. Leigh Broadhurst, Michael Crawford and Stephen Munro: Littoral Man and Waterside Woman: The Crucial Role of Marine and Lacustrine Foods and Environmental Resources in the Origin, Migration and Dominance of Homo sapiens; Chapter 2: Was Man More Aquatic in the Past? Fifty Years after Alister Hardy, Waterside Hypotheses of Human Evolution, Bantham science publishers, 2011. p. 23
[2] Bramble D, Lieberman D. Endurance running and the evolution of Homo. Nature 2004; 432: 345-52.
[3] Ruff C. Biomechanics of the hip and birth in early Homo. Am J Phys Anthropol 1995; 98: 527-74.
[4] Verhaegen M, Munro S, Vaneechoutte M, Bender-Oser N, Bender R. The original econiche of the genus Homo: Open plain or waterside? In: Muñoz S, Ed. Ecology research progress. New York: Nova Publishers 2008; pp.155-86.
[5] Klein RG. The human career. Chicago: University of Chicago Press 1999.
[6] Jacob T. Solo Man and Peking Man. In: Sigmon B, Cybulski J, Eds. Homo erectus: Papers in honor of Davidson Black. Toronto: University of Toronto Press 1981; pp. 87-104.
[7] Mania D, Vlcek E. Homo erectus in middle Europe: The discovery from Bilzingsleben. In: Sigmon B, Cybulski J, Eds. Papers in honor of Davidson Black. Toronto: University of Toronto Press 1981; pp. 133-51.
[8] Kennedy GE. Bone thickness in Homo erectus. J Hum Evol 1985;14: 699-708.
[9] Rightmire G. The human cranium from Bodo, Ethiopia: Evidence for speciation in the middle Pleistocene? J Hum Evol 1996; 31: 21-39.
[10] Wood B. The history of the genus Homo. Hum Evol 2000; 15: 39-49.
[11] Maier W, Nkini A. The phylogenetic position of Olduvai Hominid 9, especially as determined from basicranial evidence. In: Delson E, Ed. Ancestors: The hard evidence. New York: Alan R. Liss 1985; pp. 249-54.
[12] May R, Sheffer D. Growth changes in internal and craniofacial flexion measurements. Am J Phys Anthropol 1999; 110: 47-56.
[13] Lieberman D, McBratney B, Krovitz G. The evolution and development of cranial form in Homo sapiens. Proc Natl Acad Sci USA 2002; 99: 1134-9.

Homo erectus - Long distance runner?

"Most other people, including most AAT proponents as far as I can see, accept the conventional wisdom‚ that Homo erectus was a long distance runner on open savannas.This is pure nonsense: distance runners are lightly built (Arab horse, greyhound...), but erectus' skulls were twice as thick as those of gorillas, they were also more dense, with narrower marrow.Such heavy bones are very brittle (in other mammals & in human pathology). The only species with such heavy bones are slow littoral waders (heavy leg bones) &/or divers (heavy skulls).

H.erectus can't have run (or even gone) over savannas to Flores: they had to swim. This was no problem: all typically erectus features suggest frequent diving.

Whatever conventional "wisdom" tells us, long distance running is at best a very recent adaptation of some adult males a few isolated inland populations (E.Africa, Australia), with "modern" technology such as water containers etc." Marc Verhaegen

Homo erectus had stocky body shape

An international team of researchers has created the first 3D reconstruction of the ribcage of the Turkana Boy, a skeleton of the juvenile Homo erectus — the most complete skeleton of this hominin ever found — from Nariokotome, Kenya, and compared it to those of Homo sapiens and Neanderthal. Their results, published in the journal Nature Ecology and Evolution, show that the Turkana Boy had a deeper, wider and shorter ribcage than seen in Homo sapiens, suggesting Homo erectus had a stocky body shape, despite being considered the first long distance runner among our ancestors.

In the study, Professor Spoor and colleagues virtually reconstructed the ribcage of the Turkana Boy and compared it with that of modern humans and a Neanderthal.

“The results are now changing our understanding of Homo erectus. Its thorax was much wider and more voluminous than that of most people living today,” said Dr. Markus Bastir, a scientist in the Departamento de Paleobiología at the Museo Nacional de Ciencias Naturales, Madrid.

“Actually, the ribcage of Homo erectus seems more similar to that of more stocky human relatives such as Neanderthals, who would have inherited that shape from Homo erectus,” said co-author Dr. Daniel García Martínez, a researcher in the Departamento de Paleobiología at the Museo Nacional de Ciencias Naturales, Madrid, and the Centro Nacional de Investigación sobre la Evolución Humana.

The authors speculate that these changes to human body shape may have optimized breathing capabilities for long-distance running (?) and other endurance activities. (FM: with a respiratory capacity that large, what other endurance activities could they possibly mean?!)

“That Homo erectus was perhaps not the lean, athletic long-distance runner we imagined is consistent with more recent fossil finds and larger body weight estimates than previously obtained; this iconic ancestor was probably a little less like us than we portrayed over the years,” Professor Spoor said.

“Our own body shape with its flat, tall chest, and narrow pelvis and ribcage likely appeared only recently in human evolution with our species, Homo sapiens,” said co-author Dr. Scott Williams, a scientist in the Department of Anthropology at New York University.


The tall and narrow body shape of anatomically modern humans (Homo sapiens) evolved via changes in the thorax, pelvis and limbs. It is debated, however, whether these modifications first evolved together in African Homo erectus, or whether H. erectus had a more primitive body shape that was distinct from both the more ape-like Australopithecus species and H. sapiens. Here we present the first quantitative three-dimensional reconstruction of the thorax of the juvenile H. erectus skeleton, KNM-WT 15000, from Nariokotome, Kenya, along with its estimated adult rib cage, for comparison with H. sapiens and the Kebara 2 Neanderthal. Our three-dimensional reconstruction demonstrates a short, mediolaterally wide and anteroposteriorly deep thorax in KNM-WT 15000 that differs considerably from the much shallower thorax of H. sapiens, pointing to a recent evolutionary origin of fully modern human body shape. The large respiratory capacity of KNM-WT 15000 is compatible with the relatively stocky, more primitive, body shape of H. erectus.

Bastir, M., García-Martínez, D., Torres-Tamayo, N. et al. Rib cage anatomy in Homo erectus suggests a recent evolutionary origin of modern human body shape. Nat Ecol Evol 4, 1178–1187 (2020). [link]

A New Look for Early Homo

Scientists uncovered a stunning skull that gives a fresh portrait of early humans. For more on the most complete early Homo skull ever found, read the news story and research article.

Increased body size

One of the traits most commonly associated with Homo erectus is an increase in body size. The Nariokotome specimen, an adolescent male individual, was over five feet tall at the time of his death (Walker & Leakey 1993; Figures 3 & 4). Estimates of his adult stature, had he continued to live to adulthood, differ depending on how researchers estimate his age at death based on his teeth and bones (for more see Smith & Alemseged NKP article LINK HERE) and the amount of growth he had left. Living humans generally experience a marked increase in growth during early adolescence (i.e., a ‘growth spurt'), a growth pattern that some researchers say distinguishes us from other apes. If early H. erectus had a human-like growth spurt, Nariokotome likely had a lot of growing left to do. Even if H. erectus did not have such a modern human-like pattern of growth, the specimen was clearly a tall individual relative to earlier hominins. Not all H. erectus were tall, however, as earlier fossils remains from sites like Olduvai Gorge in Tanzania and Dmanisi, Georgia, attest. It is important to note that variations in size, not just an increase in size over that of earlier hominins, is characteristic of H. erectus, much like living humans.

Increased brain size/encephalization

As the body size of hominins increases, the brain size increases as well (Ruff et al. 1997). While the smallest-bodied early H. erectus fossils have brain sizes only slightly larger than earlier hominins (australopiths), early large-bodied specimens, such as the Nariokotome individual, have a brain volume greater than 800 cm3, more than 50% larger than earlier australopiths (and about 60% of the typical brain size of someone living today). However, in addition to the absolute increase in brain volume that accompanies an increase in body size, there is also a proportional increase. This is referred to as encephalization, and is an important characteristic of H. erectus. Throughout the evolutionary history of H. erectus there is substantial evidence for selection leading towards increased encephalization, so that while early members of the lineage have a cranial capacity of 600-800 cm3, the cranial capacities of most later specimens are well in excess of 1000 cm3, which is within the lower range of contemporary humans, without appearing considerably larger in body size than early H. erectus.

Increased technological/ecological intensification

The large body and large brain of H. erectus needed more energy, and thus food, than previous hominins. Larger biological structures, particularly energy-intensive ones like muscles and brains, require greater energy inputs to maintain. Thus, H. erectus is often reconstructed as occupying an intensified ecological niche (Leonard & Robertson 1997).

The intensified niche goes hand in hand with the expansion in brain and body size. Larger bodies, and longer limbs in particular, increase locomotor efficiency (Pontzer et al. 2010). Homo erectus could cover more ground on a day-to-day basis, through walking or running, than smaller hominins and with lower energy cost. In addition, the larger brain gave these hominins better capabilities for processing complex ecological information across the more expansive terrain containing higher quality food items. For example, there is clear evidence of H. erectus accessing medium- and large-sized animal carcasses for meat, through hunting and/or scavenging, in the form of fossil remains of animals with cut marks left by butchery. This behavior, regularly accessing animal carcasses, is an ecological change from earlier hominins (Link to Pobiner's NKP article). While the earliest H. erectus specimens are found in association with very basic stone tools, typically referred to as the Oldowan stone tool industry, by 1.5 million years ago populations of H. erectus were creating a more complex and typologically codified set of tools that we refer to as the Acheulean industry (Bar-Yosef & Belfer-Cohen 2001).

Reduced post-canine dentition size

The change in ecology associated with H. erectus coincides with a corresponding change in the dentition and jaws of this species. Relative to earlier australopiths and contemporary robust australopiths (Paranthropus), the size of the post-canine dentition (premolars and molars) and the molarization of the premolars are dramatically reduced in H. erectus. The corpus of the mandible (i.e., the toothless part that connects to the cranium) also displays increased gracility (i.e., slenderness), with a characteristic reduction in the relative breadth of the structure and supportive masticatory structures. Toothwear analyses suggest that across their range, H. erectus engaged in a diverse and broad diet (Ungar et al. 2006). The food an organism ingests can also produce subtle changes in the chemistry of body tissues (you actually are what you eat), including the dentin and enamel that make up the crown of a tooth. Using this information, investigations of the stable isotope chemistry of H. erectus teeth also support the idea of a flexible and diverse diet (Ungar & Sponheimer 2011). Whatever the flora and fauna H. erectus ate at the varied geographic localities where H. erectus fossils are found, their tooth and jaw anatomy reveal that their diet did not require the same robust masticatory adaptations seen in earlier hominins.

Unanswered Questions About Homo erectus

Two of the more significant, yet elusive, questions about H. erectus concern the levels of sexual dimorphism within the lineage and the capacity for language. Sexual dimorphism, the physical differences between males and females, is an important source of variation within species, and in primates can be an indicator of reproductive strategy and group dynamics. Sexual dimorphism, given its role in intraspecific variation, can also be a confounding factor in proper taxonomic identification. The large amount of size variation observed within H. erectus, taken primarily from fragmentary fossil remains, makes it difficult to estimate average levels of dimorphism. The H. erectus fossil record provides clear evidence of a large range of skeletal size variation, at least equivalent to that observed in living human populations, but it does not provide conclusive evidence that males were systematically larger than females to a greater extent than they are today. If H. erectus did have more sexual dimorphism than H. sapiens, we would infer that male competition for mates was more dependent on body size than it is today.

Language is perhaps the hallmark human trait, but can be difficult to assess directly from the fossil record. Attempts to identify language ability in the fossilized skeletal remains of H. erectus have focused on aspects of the nervous system, including the size of the vertebral canal (a proxy for the size of the spinal cord), and external features of endocasts (natural fossils of endocranial space and a proxy for brain size and shape). Thus far, there have been no definitive anatomical findings to cause researchers to reject the idea that H. erectus was capable of some kind of human-like proto-language.

More recently, arguments about the origins of language have focused on the reconstructed histories of genes associated with language production in humans. The recovery of ancient genetic sequences from Neandertals and other archaic human specimens (e.g., a specimen from Denisova Cave in Siberia, Russia) have provided new insight into the genetic history of language production. The human FOXP2 gene exists in a derived form in humans today and appears to play a critical role in language development. The identification of the human form of FOXP2 in both Neandertal and Denisovan genomes suggests this gene likely goes back at least to the Middle Pleistocene, with H. erectus a possible source lineage (although there is no H. erectus ancient DNA to test this hypothesis). This does not suggest H. erectus had well-developed language capabilities but, like the anatomical evidence, does not provide any evidence to reject the idea.


Homo erectus represents a significant transformation from previous hominins, like the australopiths, to a species much more similar to modern humans. Relative to their australopith forebears, Homo erectus was bigger, smarter, and more able to occupy and survive in differing landscapes in a changing world. The movement towards a more ecologically intense, cognitively reliant, and behaviorally malleable adaptive pattern set the stage for the evolutionary change that followed in the Pleistocene, up to and including the present. In many ways, modern humans are just an updated version of our H. erectus ancestors.



Acheulean artifacts discovered on isolated islands that were never connected to land in the Pleistocene may show seafaring by H. erectus as early as 1 mya in Indonesia. They had arrived on the islands of FloresTimor, and Roti, which would have necessitated crossing the Lombok Strait (the Wallace Line), at least before 800 kya. It is also possible they were the first European mariners as well and crossed the Strait of Gibraltar between North Africa and Spain. Seafaring capability would show H. erectus had a great capacity for planning, likely months in advance of the trip.[98][99]


Website: F. Mansfield, 2015

Disclaimer: This site is currently under construction. Every effort has been (will be!) made to trace the copyright owners of any images or text used on this site to request permission and to give proper credit. If you are the copyright holder of any images, files or text and have not been contacted, please contact the webmaster in order to rectify this.