aquarboreal & littoral theories
- From: Marc Verhaegen <m_verhaegen@xxxxxxxxx>
- Date: Sat, 30 May 2009 18:30:21 +0200
Littoral diets in early Hominoids and/or early Homo?
Marc Verhaegen & Stephen Munro 2009
Fish & Seafood, 28th ICAF Conference, Kamilari, Crete, 31 May 6 June 2009
Evidence is accumulating that human ancestors evolved at the edge between
land and water, rather than on dry open plains (comparative, anatomical,
physiological, nutritional, biochemical, molecular, fossil,
paleo-environmental, geological data):
1. Hominoids descend from vertical aquarboreal frugi-omnivores (google
?aquarboreal¹):
Gorilla and orangutan population densities are highest in swamp forests
(Ndoki, Mbeli, Suaq). Mio-Pliocene apes (Helio-, Gripho-, Dryo- and
Oreopithecus) are typically found in coastal and swamp sediments around the
Tethys Sea, the ancient Mediterranean Sea. Comparative and fossil data (the
Moroto lumbar vertebra) suggest that apes ~20 Ma had already adopted a
vertical locomotion and spine, which included arm-hanging from branches and
wading bipedally as is seen in lowland gorillas feeding on aquatic herbs in
forest bais. Great apes make and use tools, and most fossil great apes had
thick enamel, suggesting their ancestral diet included hard-shelled fruits,
nuts, invertebrates etc.
2. Humans descend from littoral durophagous omnivores:
After the split with Pan ~5 Ma, Homo ancestors apparently became littoral
omnivores (arguably on the continental shelves, when glacial sea levels were
lower than today) who beach-combed, waded and dived for waterside and
shallow water foods such as shellfish, coconuts, crabs, turtles, eggs,
stranded whales, drowned bovids etc.:
a. Modern humans show (ex)semi-aquatic features:
Features that are seen in humans but not chimpanzees include: a huge brain,
voluntary breathing control and slow-diving skills, hyoid bone descent, a
small mouth, projecting nose and poor olfaction, a body build with head and
spine and legs on one line, flat feet with first digital rays longest,
extensive subcutaneous fat tissues, abundant thermo-active sweating and loss
of body fur, multi-papillary kidneys and in the fetus renculated kidneys,
etc. These features in different combinations are seen in waterside and
semi-aquatic animals, but not in typical savanna animals.
b. Archaic Homo populations dispersed along the seashores:
Independent data suggest that the Plio-Pleistocene diaspora of Homo happened
along the sea-coasts, and from there inland along wetlands, lakes and
rivers:
· The anatomically very aberrant Homo floresiensis specimens as well as
retroviral data suggesting that human ancestors were absent from Africa
between 4 and 3 Ma are arguments for a long-standing presence of Homo
ancestors at South Asian coasts.
· Archaic Homo skeletons, to different degrees, had very dense and
thick cranial and postcranial bones and bone cortex. This is only seen in
littoral species that collect sessile aquatic foods.
· Some Homo erectus and Homo neanderthalensis had auditory exostoses,
which in modern humans are typical of divers and surfers in cold water.
· Palaeo-environmental data show that most or all fossil Homo remains
derive from waterside milieus with large bodies of water and abundant edible
molluscs.
· Durophagous mammals (feeding on hard-shelled foods, e.g. shellfish)
often display thick enamel as well as well-developed dexterity and tool use
features prominent in fossil Homo species.
· Brain enlargment, seen throughout the evolution of Homo, requires
poly-unsaturated long-chain fatty acids that are abundant in aquatic foods,
e.g. DHA.
Pachyosteosclerosis suggests archaic Homo exploited sessile littoral foods
Stephen Munro & Marc Verhaegen 2009
Fish & Seafood 28thICAF Conference
http://utopia.duth.gr/~xirot/28thICAF/ICAF.html
The cranial and postcranial bones of Homo erectus and other archaic Homo
fossils throughout the Pleistocene (~1.8 Ma to 10 ka), from Africa, Europe,
South and East Asia, were typically very heavy, displaying
pachyosteosclerosis: pachyostosis (thick bones), osteosclerosis (compact
bone cortex) and medullary stenosis (narrow marrow canals).
Pachyosteosclerosis is often used to help identify Homo erectus fossils:
other primates, fossil or extant, including apes and australopithecines,
lack this feature, and even outside the primate order, animals with such
massive skeletons are rare (Table).
A review of the occurrence of very heavy bones in other tetrapods
suggests that they are more brittle than bones of the usual histology, but
have a hydrostatic ballast function. Wading species such as hippos and some
pakicetids (Eocene 'whales') show heavy limb bones (Table); slow-diving
species for sessile littoral foods such as extinct and extant walruses and
seacows typically have heavy skulls.
Therefore, we consider whether archaic Homo populations collected
shellfish through parttime wading or/and shallow-water diving when they
dispersed to different continents along the coasts, and from there inland
along rivers or lakes. Palaeo-ecological reviews confirm that most, if not
all, archaic fossils/tools are associated with large bodies of permanent
water and water-dependent edible molluscs,
http://users.ugent.be/%7Emvaneech/Verhaegen%20et%20al.%202007.%20Econiche%20
of%20Homo.pdf.
We discuss the alternative hypotheses for pachyosteosclerosis in the
literature heavy exertion, endurance running, fighting with large prey, or
protection against intraspecific violence as well as some apparent
exceptions to the rule, such as thin-boned Homo erectus (e.g. KNM-OL 45500)
and thick-boned Homo sapiens (e.g. Kow Swamp).
Since fresh and salt water densities differ, heavy skeletons in
Homo erectus as well as some Homo sapiens populations might have been
correlated with dwelling along salt lake or sea shores (including Out of
Africa episodes). Arguably there existed cyclic adaptations during the Ice
Ages, with Homo populations generally becoming more beach-combing, wading
and diving and relying on shellfish on the continental shelves during
glacials (with sea levels up to 120 m lower than today), and shifting to
more inland waterside dwelling, seasonally or more permanently, during
interglacials.
Cranial pachyostosis
parietal eminence thickness (mm)
(Kennedy 1991)
Gorilla gorilla 3.6
Pan troglodytes 5.3
Australopithecus africanus 5.6
Homo neanderthalensis 8.1
Homo erectus 10.6
Homo sapiens 5.6
Medullary stenosis
midshaft cortex / femoral width (%)
(Thewissen cs.2007, Aiello & Dean 1990)
Saiga tatarica, bovid ~30 kg 68
Ichthyolestes pinfoldi, pakicetid 25
Nalacetus ratimitus, pakicetid 54
extant apes ~10 to 100 kg 58
archaic Homo KNM-ER 1481 26
Homo sapiens, modern humans 42
.
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