Re: Waking up covered in dew

Nick Maclaren (
4 Sep 1996 13:46:31 GMT

In article <>, Paul Crowley <> writes:
|> In article <01bb9288$f31a1140$>
|> "Philip Nicholls" writes:
|> > Paul Crowley <> wrote in article
|> > > As you imply, my basic point stands. Sleeping naked on the ground
|> > > you'd get chilled to death.
|> >
|> > Paul, does it occur to you that there may be a reason why apes build
|> > nightnests and that early hominids, naked or not, very likely did the same
|> > (as we still do today).
|> We've already covered this point, Phil, in this very thread.
|> Apes built nests in trees and rest *on* them. They do this to
|> avoid predators, not to avoid cold.

True, but not the whole truth.

|> Would you sleep up in a tree in order to avoid cold?

Yes, and I do! In radiative conditions (e.g. savannah and not
jungle), the coldest air is near the ground (i.e. exactly the
converse of during the day). A hammock is often warmer than a
tent, as I can witness - though much of that is due to reduced
conduction through the ground.

|> Large male gorillas sleep on the ground,
|> usually first covering it with vegetation against dampness on the
|> ground.

But large males aren't the issue. If there is one cold spell every
10 years severe enough to kill even 10% of immature animals, this is
a massive evolutionary pressure. Any mutation that halves this
death rate could have significant disadvantages and still spread
throughout the population over hundreds of millenia.

|> For significant protection against cold, you need a
|> layer of impervious material to trap a warm layer of air. Loose
|> vegetation is not much use.

It does not have to be impervious, and is best if it is not.
Impervious material causes condensation. All it has to do is to
trap enough air to slow convection (including wind). Many small
animals use loose vegetation as insulation, and it is a standard
survival technique.

Nick Maclaren,
University of Cambridge Computer Laboratory,
New Museums Site, Pembroke Street, Cambridge CB2 3QG, England.
Tel.: +44 1223 334761 Fax: +44 1223 334679