There are still some idiots who believe
in snorkel noses...
OI, BIG NOSE !
New Scientist 2782 p 69 Lastword 16 October 2010
Why do humans evolve external noses that don’t seem to serve any useful purpose – our smelling sensors are inside the head. Our nose is vulnerable to damage, and the majority of primates and other mammals manage with relatively flat faces.
Traditional explanations are that the nose protects against dry air, hot air, cold air, dusty air, whatever air, but most savannah mammals have no external noses, and polar animals such as arctic foxes or hares tend to evolve shorter extremities
including flatter noses (Allen’s Rule), not larger as the Neanderthal protruding nose.
The answer isn’t so difficult if we simply consider humans like other mammals.
An external nose is seen in elephant seals, hooded seals, tapirs, elephants, swine and, among primates, in the mangrove-dwelling proboscis monkeys. Various, often mutually compatible functions, have been proposed, such as sexual display (in male hooded
and elephant seals or proboscis monkeys), manipulation of food (in elephants, tapirs and swine), a snorkel (elephants, proboscis monkeys) and as a nose-closing aid during diving (in most of these animals). These mammals spend a lot of time at the margins
of land and water. Possible functions of an external nose in creatures evolving into aquatic ones are obvious and match those listed above in many cases. They can initially act as a nose closure, a snorkel, to keep water out, to dig in wet soil for food,
and so on. Afterwards, these external noses can also become co-opted for other functions, such as sexual display (visual as well as auditory) in hooded and elephant seals and proboscis monkeys.
But what does this have to do with human evolution?
The earliest known Homo fossils outside Africa – such as those at Mojokerto in Java and Dmanisi in Georgia – are about 1.8 million years old. The easiest way for them to have spread to other continents, and to islands such as Java, is along the
coasts, and from there inland along rivers. During the glacial periods of the Pleistocene – the ice age cycles that ran from about 1.8 million to 12,000 years ago – most coasts were about 100 metres below the present-day sea level, so we don’t know
whether or when Homo populations lived there. But coasts and riversides are full of shellfish and other foods that are easily collected and digested by smart, handy and tool-using “apes”, and are rich in potential brain-boosting nutrients such as
docosahexaenoic acid (DHA).
If Pleistocene Homo spread along the coasts, beachcombing, wading and diving for seafoods as Polynesian islanders still do, this could explain why Homo erectus evolved larger brains (aided by DHA) and larger noses (because of their part-time diving).
This littoral intermezzo could help to explain not only why we like to have our holidays at tropical beaches, eating shrimps and coconuts, but also why we became fat and furless bipeds with long legs, large brains and big noses.
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