The AAH argument for tears has always been, at best, a peripheral one. Hardy
never even mentioned it and Morgan's early attention to it perhaps was
misguided. She all but withdrew her support for the idea in her latest book.
Moore does make some, rather slight, kind of concession to
this fact early in the page, writing "some proponents of the AAT have moved
away from the idea that the aquatic phase was in a salt water environment"
but, nonetheless goes on to make the unsupported claim that "but most still claim humans' sweat and tears
systems evolved as an aquatic feature, as an excretory system for salt."
In fact he all but ignores his own admission that this is really a non-topic
because he goes onto to write nearly 5,000 words and 84 paragraphs on the subject.
This is roughly twice as much as two of the major pillars of the AAH were
afforded. Moore wrote about 2,000 words and 30 paragraphs on hairlessness;
about 3,000 words and 33 paragraphs on fat (actually only about 1,800 words and 15
paragraphs if you take away the copious quotations from Pond); and 0 on
On this page, Moore makes
claims about the AAH
on the subject of tears. One is wrong in its factual basis as it does
not take into account Morgan's clear renouncement of the idea in 1997 (see point 2)
and one is clearly correct, although Morgan has clearly backed away
from her earlier position on this too (point 1).
Moore is correct to argue that the evidence in tears
does not appear to support the AAH. However, as Morgan has pretty much
conceded that herself in her last book, and most other proponents of the
theory have never claimed tears did support there case, it is rather a mute
Perhaps the most significant aspect of this page is
the fact that Moore continues to maintain it as a major part of his AAH
refutation, seven years after the fact that Morgan all but withdrew her
support for the arguments it contains.
Moore's initial point on this page seems to be an attempt to ridicule supporters of the
hypothesis, claiming that they still consider salt tears would have evolved
as an excretory mechanism even if they lived in fresh water habitats.
Without a citation to back this claim up, however, this really should be
seen as just gossip.
Tears and the AAT
Moore starts with a quote from William Frey in which he basically says that
he thinks only humans (my emphasis) have ever been observed to
exhibit emotional tears. Moore probably wants to draw attention to the fact
that Frey doesn't mention aquatic mammals here, only humans. Morgan quotes
the same authority in her books (Moore even gives a reference to one such
citation, but not to any of her claims) on this subject but Moore suggests
that her citing of his work is misleading. He writes "Dr. Frey has done
studies of emotional tears and Morgan feels support they her theory. Why she
feels they support her is rather inexplicable, once you look at the
evidence, including the evidence in the book which Morgan cites."
Moore says the two AAH claims here are that:
1) "this particular AAT idea, initially promoted by Morgan and since
repeated many times by AATers, is that emotional tears are seen only in
humans and aquatic animals" and
2) tears "...(and our sweat glands) evolved as system to excrete salt."
and he deals with the two claims separately on the page
But before we follow his arguments, perhaps we should
question his starting point. Are these actually the claims made by Morgan
or other AAH proponents?
In 'Scars of
Evolution' Morgan introduces the idea of weeping salt tears thus: "Marine
reptiles, and some marine mammals, encountering the same problem [the need
to excrete excess salt], deal with it not by nasal dripping [as with marine
birds] but by weeping salt tears, for example, marine iguanas and turtles,
marine crocodiles, sea snakes, seals and sea otters." Morgan (1990:96.) No
mention of emotional tears there but on the next page she does imply it when
she wrote "The connection between weeping to excrete salt and weeping from
emotion is not easy to understand, but it an ancient one. There are accounts
of copious nasal dripping in seagulls in situations of aggressive
confrontation, and weeping in sea otters when distressed or frustrated. The
stimulating hormone prolactin, which appears to be involved in human weeping
is released in response to emotional stress" (Morgan 1990:97).
In her latest book, Morgan clearly backs away from this salt tears argument
and it could be argued that Moore should therefore have withdrawn it too.
However Morgan did write "But humans also weep tears which have nothing to
do with local irritation of the eyeball. Darwin called them, rather
picturesquely, 'psychic' tears. A more neutral term would be simply
'non-reflex' or 'emotional' or 'non-irritant', and it seemed to me that they
were not without analogues in the animal world." (Morgan 1997:103.) She
quotes from Schmidt-Nielsen's (1959) paper that, like marine birds that
excrete salt from nasal glands "there are similar salt-excreting organs in
marine crocodiles, marine iguanas, sea snakes and marine turtles. In all of
these cases the brine is excreted from the eyes in the form of salt tears.
If the creatures are induced to ingest salt water, the tears are activated."
So, perhaps we should give Moore the benefit of the doubt
here. Morgan does seem to still be arguing that there is something rather
unique about human tears which tends to be shared by more aquatic animals.
The second claim, that tears evolved
as a system to excrete excess salt, is less ambiguous.
Morgan clearly withdrew her support for
that hypothesis in 1997. She wrote "I made the suggestion [In Scars..] that both
the tears and the sweat might have been at one time more concentrated than
they are now, and evolved originally for the excretion of salt. I was almost
certainly wrong about that..." Morgan (1997:102). And "On balance, then, I
am inclined to concede that the excretory hypothesis of tears was
misconceived." (Morgan 1997:108). She concludes "Despite the lump in the
throat, the original AAT theory of tears has flaws in it. If there were any
other theory available that had no flaws in it it, then that would settle
the matter" Morgan (1997:108.)
Moore's site was last updated early 2004 but he has not yet amended this page accordingly. Instead it remains, at the time of
writing (March 21st 2004) seven years after Morgan published those
statements, as a critical indictment on her work and the AAH itself.
shed emotional tears?
Moore begins this section by drawing upon
Frey's Chapter 14, basically to show that Morgan was economical with the
facts that she chose to report in her 'Scars of Evolution' account.
Specifically, Moore claims that Morgan omitted dogs, wolves, lab rats and
gorillas from her citation. It's true that she did specifically list certain
aquatic animals, which Frey referred to, without mentioning the others and
this might be interpreted as being somewhat economical with the truth. but
it should be noted that her point was made before the Frey reference.
However, this is impossible to defend. It does taint her work with the feeling that
on this occasion she valued getting over her argument
more than the accuracy of the content she was using to back that argument
I think, however, that this was an isolated case of misrepresentation. It's a great
pity that she did so but it does not make all of her ideas wrong and, should, at least, be judged alongside some of the misrepresentations Moore has made
himself on his web
summarises the section thus: "So we can see that there is every bit as much,
and as little, evidence for non-aquatic animals shedding emotional tears as
there is for aquatic animals. This is contrary to Morgan's claims in print,
as well as the claims Morgan and others have made repeatedly in the
sci.anthropology.paleo newsgroup and other online forums." and it appears he
may be right.
However, for many proponents of some kind of AAH this is no problem to the
hypothesis as a whole.
excretory abilities of the lacrimal (tear) glands
The second part of this web page is almost irrelevant, since Morgan has
clearly withdrawn her support for the idea that salt tears in humans could
be a remnant of salt excretion from an earlier aquatic phase.
completion's sake, Moore's criticisms will nevertheless be evaluated.
introduces the subject by claiming that Morgan's understanding of
classification of tears into two distinct types was confused. She
claimed that the two types were 'psychic' or emotional tears and 'reflex'
tears whereas, actually, the two types are 'basal' and 'reflex' tears.
Apparently 'psychogenic' tears are classified under the 'reflex' type.
Perhaps Morgan did get the minutia of the taxonomy wrong but the important question
remains: Is there any difference between the composition of 'psychogenic'
tears and the composition of other types of reflex tears? It was that
difference that Morgan was arguing might provide a clue to a more aquatic
ancestry in humans. And it was that difference which Morgan claimed Frey
point argues that as human lacrimal glands cannot actively excrete sodium
today it is unparsimonious that they should have evolved this ability in the
past for a period and then lost that ability again. Nobody could argue with
In the next section Moore goes on to provide several quotes which show that
human lacrimal glands are capable of active excretion of potassium (4x serum
levels) and manganese (30x). There's also a quote from Frey showing no
significant difference between 'phsychogenic' and other 'reflex' tears in
mangansese levels but nothing regarding the other ions.
section, entitled 'innervation of tear secretion', argues that the active
excretion of potassium by human lacrimal glands actually more closely
parallels terrestrial animals such as ostriches
Moore finishes the page with a section on homeostasis where he outlines that
the main principle of salt excretion is that a hypertonic solution has to be
generated for it to work. He makes some good points, for example, arguing
that the main organ of homeostasis is the kidney and this organ has
developed further in mammals than other animals. He goes to great lengths to
argue that as human tears and sweat cannot do not have this property it
cannot be a plausible mechanism for salt excretion.
He ends by writing "By the way, all this info was available long before even
Hardy wrote up his AAT paper; even longer before Morgan did her first book
on the subject. Was Morgan aware of it? I got the reference to Weiner and
Hellman's research from her; she quoted them. So she had the info in her
hand that proved her contention to be wrong even as she wrote it up." This
is a rather disingenuous point as Morgan made it clear that she was arguing
that the use of lacrimal glands for some types of excretion today may have
been indicative of a slightly different use in the past.
Moore ends the
page with several references emphasising the use of kidneys in marine
mammals in osmoregulation.
It should be noted that, once again, the comparisons that matter should be
with chimpanzees and gorillas and not with seals and dolphins. If human
kidneys turned out to have a better excretory function than our nearest ape
ancestors then that should be an observation which is explicable by some
parsimonious storyline. If their function was not significantly different it
would suggest that there is really nothing to explain.
Moore makes a rather good case that as the human lacrimal glands are not
capable of the excretion of sodium then it is rather unparsimonious to
suggest that they would have evolved the ability to do so for a period of
our evolution only to revert back again afterwards. He also makes some very
good points that even marine mammals which, like desert animals, are most
concerned with salt excretion have evolved very efficient lobulated kidneys,
to perform this excretion, and not done so through either sweating or the
shedding of tears.
These would be winning arguments in this debate if Morgan had not already
conceded to them in 1997.
Denton, Derek; Weisinger, R; Mundy, NI; Wickings, E J; Dixson, A; Moisson,
P; Pingard, AM; Shade, R; Carey, D; Ardaillou, R; Paillard, F; Chapman, J;
Thillet, J; Michel, J B (1995). THE EFFECT OF INCREASED SALT INTAKE ON
BLOOD-PRESSURE OF CHIMPANZEES. ?Nature Medicine Vol:1 (10) Pages:1009-1016)
Morgan, Elaine (1990). The Scars of Evolution. Oxford University Press
Morgan, Elaine (1997). The Aquatic Ape Hypothesis. Souvenir Press
Schmidt-Neilsen, Kurt (1959) Salt Glands, Scientific American, 200
H. Frey and Langseth, Muriel (1985): Crying: The Mystery of Tears
Minneapolis: Winston Press.