Re: Fleas and AAH

Keith Norris (keith@GECKO.BIOL.WITS.AC.ZA)
Sat, 29 Jun 1996 09:42:19 LOCAL

Whee! My account is still up! Going any day now, though *sob*.

This reply asks more questions than it tries to answer, I'm afraid.

In article <keith.52.002586F0@GECKO.BIOL.WITS.AC.ZA> you wrote:
: Paging through the introduction to Desmond Morris' "The Naked Ape" I came
: across this interesting piece:

[quotes hacked]
: My question is this - surely an aquatic ape would not have had a problem with
: fleas as they could not have survived the long periods in water postulated by
: the AAH?

Hmm... possible reason behind this could go something like:

We have lost our fur anyway, right? Apart from the head hair, and pubic
hair, and the hairier chests of males, (which I am inclined to think came
later after a northward migration anyway). So, unless we were already
clothed by this time, the fleas would be unable to cling to us.

So we need somewhere where they can live and grow and not get caught, and
crawl out and know we would be there to bite.

But, if we had lost our fur, we are more likely to need comfortable
bedding, right? And the fleas are used to living and breeding in the
bedding anyway, so that's not a problem.

So, since we are hairless, all the fact that we have fleas tells us is
that we stayed in the same place long enough to allow fleas to breed in
our bedding.

Although this seems in opposition to many of the theories opposing the
AAT, which would fit better the pattern of a nomadic lifestyle, I see no
reason why a creature hunting berries or whatever during the day cannot
return to a predefined base, particularly if it were in a nice spot and
with comfortable beds prepared. I thought gorillas did this anyway,
(sleeping in 'nests'), but I may be mistaken.

However, it does tell us that if we were aquatic, then we were probably
fixed to one home base for fairly extended preiods of time.

: The fleas would not have had time to evolve into this species
: there-after (I don't think). This goes hand-in-hand with a very early
Since I think the AAT says that we were aquatic for a good deal
less time than we have since been non-aquatic, the fleas could be a later
addition. After all, as you say,
: host-parasite interactions and co-evolution are [...] extremely rapid

I'm curious, though. I have heard of cat fleas and dog fleas, but never a
human flea before. Is this because they are uncommon in the UK?

: criticism of the theory, written in the letters page of the New Scientist 7
: (1960), pg 889 in direct response to Sir Alister Hardy's paper. The author of
: the letter, H.B.N. Hynes, points out that man has no parasites which are
: associted with salt water, unlike marine birds, seals, whales and other marine

Hmm... OK, I admit to utter ignorance here. It sounds a pretty good and
valid criticism.

Just to demonstrate my utter ignorance of parasites (I'm an Engineer, not a
doctor!), what is a liver fluke? I thought these were something to do
with the water anyway.

Also, is it possible to catch any parasite from eating fish? Shellfish?
This is most likely to have been our major meat source.

There are several 'ports' through which an aquatic parasite could attack
us. The first and most obvious is the skin, either sucking blod through
the skin, burrowing through it, or laying aggs under it. All these have
been noticed on land, though the 'human flea' is the first parasite I
have heard of that is designed specially for the task.

Next comes the mouth. This is usually closed when swimming, so this would
only work if the parasite were in the fish/shellfish/seaweed we ate.

Finally, nose, anus and genitals (ears are a subset of skin from what
I can see). Any parasite using these ports needs to be able to 1) find
them, which requires accuracy or large numbers and the blind luck that
one or two might get in, 2) the strength to get in, since all ports
are held shut (though the nose is held shut inside), and 3) the subtlety
to get in without being noticed. For these reasons, I think only very
small parasites would be able to take advantage of this, and they would
be unable to support the required numbers just by targeting humans.

So, basically, is there anything that bites us underwater, and can we
catch anything from aquatic food? If so, then I reckon it would classify
as an aquatic parasite.

Is athlete's foot unique to humans, or is it just one form of a fungus
that can take several?

: animals. It would be expected that if we had a long period of marine
: habitation, we would find marine organisms being intermediate hosts for
: parasites of our species. Hardy replies (in the same issue) that if man

I think this unlikely. We have been out of the water for, what, ten,
twenty million years? (One day I'll get this timeline straight in my
head). Any parasites we did have in the water would have had to find some
other source of sustenance in that time and forget about us completely.
And I find it unlikely that there were neough aquatic apes to make preying
on them exclusively a profitable passtime for a parasite: the odds of
finding a new one if something happenned to the current one would be very
low.

But I am surprised indeed if there are no parasites that come up and
latch onto people in the water. Leeches in freshwater are obvious. But
what about saltwater? Is there no equivalent niche there? (I think sharks
are too big to qualify as parasites. Of one of them came up and latched
onto you you'd be in trouble).

: retained his habit of defecating on the land then there would more than likely
: be no problem ITR, as faeces would rarely find their way back to the sea.

Can aquatic creatures get tapeworm?

Wouldn't the intervening 20-odd MY have removed all traces of an aquatic
parasite that required us as a link in it's chain?

: However, he also claimed that if man had kept the aquatic mode for a long time
: then selection would have worked against his susceptability to such parasites.
: This is clearly false because, as Hynes showed, the other marine organisms

Yup. Sounds like one of his less inspired pieces of reasoning.

But then, I have probably demonstrated my own awful powers of reasoning
above, being as I know nothing about the study of parasites at all.
Perhaps someone better versed in it all could help me out.

--

 - D.                                        http://www.brad.ac.uk/~dmorgan/