In the section on tears you'll
find that AAT/H proponents claim tears in humans are a method of actively excreting
salt in response to a saltwater environment, but in fact, tears are never
hypertonic and cannot do what AAT/H proponents claim for them.
Tears are, however,
strongly hypertonic in regard to potassium and that does indicate
what environment we developed in.
That environment is terrestrial,
The salt glands of terrestrial birds and reptiles
are specialized for excreting potassium, unlike those of their marine relatives.
Some AAT/H proponents, most notably Elaine
Morgan, have insisted that salt glands do not exist in terrestrial birds
I must admit I find it discouraging that someone who
is making up a theory with which they wish to supplant the past several
decades of paleoanthropology does so little research before making such
This info is readily available.
Of course, it may be that it
isn't simply poor research, since Morgan continued to make the "salt glands
only in marine birds and reptiles" claim long after the facts (with refs
and accurate quotes) had been presented to her (in several newsgroup posts
which she replied to and so presumably read).
She did finally say
that she was dropping these bogus claims, but these are related to her
claims that human tears and sweat are aquatic adaptations, and she and
other AAT/H proponents still make those claims.
As always, the "false facts"
generated by AAT/H proponents are persistent, and so I feel the facts must
be stated once again.
1975 Salt Glands in Birds
and Reptiles by M. Peaker and J.L. Linzell (Dept. of Physiology, Agricultural
Research Council, Institute of Animal Physiology, Babraham, Cambridge).
Monographs of the Physiological Society No. 32.
Press: Cambridge, London, New York, Melbourne.
Mentioned in text:
Some terrestrial birds with
2. a Partridge, Ammoperdix
heyi (North Africa and the Middle East
3. various Falconiformes (birds
of prey), including Red-Tailed Hawks
4. North American Roadrunner,
Some terrestrial reptiles with
1. Green or Linnean Iguana,
2. Desert Iguana, Disposaurus
dorsalis (North America)
3. at least one variety of
Mastigure, Uromastyx aegytius (North Africa and the Middle East
5. False Iguana, Ctenosaura
Table 13.3. Salt glands in
Nasal salt secretion observed
Iguanidae Iguana iguana
Agamidae Uromastyx aegytius
Scincidae Eumeces skiltonianus
Xantusidae Species not stated
Teiidae Species not stated
Varanidae Varanus gouldii
Nasal salt secretion not observed
Agamidae Amphibolurus ornatus
Lacertidae Lacerta viridus
Other families with representatives
lacking salt glands:
Anniellidae, Teiidae, Cordylidae,
The evolution of salt
glands, or indeed of any homeostatic system, is clearly a fascinating subject
Cranial salt glands are only known to exist in birds
and modern reptiles.
Therefore it is the reptiles to which we must
concentrate most of our attentions.
Nasal glands probably first appeared
in the Amphibia serving to moisten and cleanse the nasal passages of the
adults, which are usually terrestrial (see Bang & Bang, 1959). Judging
by extant species the kidneys of reptiles and birds are much less 'efficient',
in terms of concentrating ability, than those of mammals. Therefore evolution
of amphibian nasal glands into salt-secreting glands might be inferred
to have occurred in the early reptiles since, in truly terrestrial vertebrates,
two major avenues for ionic and osmotic regulation present in lower vertebrates
would have been lost -- the gills and the skin. In fact the development
of the reptilian skin, which is relatively impermeable, from the amphibian
type across which ions and water movements occur and can be controlled,
must have meant a major alteration in the control of salt and water metabolism.
Therefore any animal with an additional means of excreting ions would be
at an advantage. It would enable such creatures to live on plants, which
are rich in potassium and/or return to the sea and eat plants and invertebrates,
which have the same ionic content as sea water. Therefore one might argue
that the evolution of a salt gland together with all the other adaptations
which enabled the initial colonization of land, was an important means
of permitting the vast and complex adaptive radiation that occurred to
fill all the varied ecological niches.