Re: Faithful Ancestors was Re: Doesn't ANYONE have anything new to say?

rmacfarl wrote: 
Lorenzo L. Love wrote:
...

http://dept.kent.edu/anthropology/love.html 

...

And besides, how valid is this big males equals harems thing? Any of
these people ever see a male orangutan?

Lorenzo L. Love
http://home.thegrid.net/~lllove

"Facts are meaningless. You can use facts to prove anything remotely true."
                           Homer Simpson



Nice pickup. However I'm not in your camp, or Lovejoy's about sexual
dimorphism. Even when I first read of his food-sharing hypothesis in
Johanson's Lucy's Child, it just struck me as a too anthropomorphic
picture of a still very ape-like animal.

As re orangs, the key point is that male size equals reproductive
access to females. Orangs are polygamous & big males win out in the
race to reproduce. Humans & chimps exhibit less dimorphism, and males
have less success at monoplising access to females (with differing
strategies) than orangs & gorillas.

The only thing that to me argues in favour of less competition between
males is reduced canine size. But I must say when it's so rare to find
a statistically significant sample of fossils from a single species in
a single moment in time, as the First Family appears to be, then
evidence that there appears to be significant dimorphism within it as
persuasive. I stand to be re-educated, but I find Lovejoy's latest
analysis unconvincing and a little too much like "well he would say
that, wouldn't he?"

(And if this doesn't stir up a good verbal stoush, I'm giving up on you
lot as a bad job... :-)

Ross Macfarlane


Significant dimorphism within the First Family? Not according to Lovejoy:
"Whether the First Family included two dozen or only a half-dozen
members, males exhibited a moderate size advantage over females, close
to that observed in people, Lovejoy's team found."



That's one view. Here's another in the same article:

"Plavcan and his colleagues determined the relationship between various

skeletal measures and body mass for 658 people from eight populations
in
different parts of the world. With those correlations, the team made
new
calculations of femur-head size and body mass for seven A. afarensis
specimens not in the First Family and assigned sex on the basis of
size.

This work reveals sex differences considerably greater than those in
people and approaching those in gorillas, according to Plavcan's team."


"and assigned sex on the basis of size."
That's the same circular reasoning McHenry used, Plavcan just confuses the matter by using femur-head size instead of overall size. It's still separating the bones into two piles based on size, arbitrarily assigning the big bones as male and the little bones as female. All you really have is two piles of bones, sex unknown. Maybe most of the big bones are male but there's likely to be a few Gabriele Reese in there and maybe most of the little bones are female but there's likely to be a few Danny DeVitos in there. Every misidentified bone inflates the dimorphism amount.

The proper methodology would be to determine sex first by indisputable anatomical structure, not gross size, then measure the comparative sizes of the two sexes. Disregard any bones who sex can not be determined without regard to size. That's not going to happen because there just isn't enough intact pelvises around. There is still disagreement over Lucy's sex because her's or his pelvis was so badly busted up. The assumption is she's female because she's so small, but it's just an assumption not a fact.


Since those love them and leave them guys, orangutans, and the faithful
and protective good husbands, gorillas, both show similar high levels of
dimorphism, what can we conclude about group behavior vs dimorphism?
Zip. Both the orangutan model and the gorilla model may provide a sexual
monopoly for the male (not so much with gorillas, observation shows lots
of females sneaking off into the bushes with the younger males) but the
two models are diametrically opposite in regards to group dynamics. So
for those who make the poory support claim of high dimorphism, why
assume the gorilla model? Because male gorillas seem to be nicer people
then the asocial male orangutans who basically rape their wimen folk?



You misinterpret the relationships. In both gorillas & orangs, a few
large males monopolise access to many females. In chimps, females are
less likely to mate with the alpha male of the group, so competition
based on being the biggest & ugliest on the block is much less intense.
And bonobos, of course, put it about whenever, wherever & with whoever
they like.

An orangutan can only monopolize one female at a time. One after another maybe if he's got the stuff, but just one at a time. A gorilla, in theory, can monopolize several females at once. And so very different social structures in spite of similar levels of dimorphism. Chimpanzees and bonobos as you note have different social structures but similar levels of dimorphism. So what does dimorphism tell us about social structures? Not a lot.



But we have no idea of what the dimorphism is. When two leading
researchers take the same data and come up with two such widely
diverging conclusions, there is something wrong. Lovejoy's methodology
may not be perfect, but McHenry and Plavcan's circular reason is
obviously fundamentally flawed.



On the contrary. McHenry & Plavcan's hypotheses have analogies in
well-established primate models - e.g. babboons vs patas monkeys,
whereas Lovejoy's work is an exercise in hippy food-sharing wish
fufillment.

(Ooh, them's fighting words... :-)

What does Occam's Razor tell us? As both Homo and Pan have similar
moderate dimorphism, what must we assume about the last common ancestor?
And for any species in the lineage between that LCA and the present?



Occam's razor tells me that when you have 2 great apes who are
morphologically as similar, with lifestyles as radically different, as
chimps & bonobos, you postulate early hominids' behaviour at your
peril...

Ross Macfarlane


That's right, behavior is so fluid and changeable, especially sexual and social behavior that it will probably alway be a mystery but physical characteristics like dimorphism can be determined with sufficient data (which we don't have yet). It just won't tell us much about behavior.

Meanwhile Occam's Razor tells us the default assumption should be that afarensis probably had similar levels of dimorphism that the species most closely related to them have. McHenry and Plavcan's contorted analysis not withstanding.


Lorenzo L. Love
http://home.thegrid.net/~lllove

“Facts are meaningless. You can use facts to prove anything remotely true.”
                            Homer Simpson


.

Relevant Pages

  • Re: Faithful Ancestors was Re: Doesnt ANYONE have anything new to say?
    ... > the big bones as male and the little bones as female. ... Every misidentified bone inflates the dimorphism amount. ... >>>of females sneaking off into the bushes with the younger males) but the ...
    (sci.anthropology.paleo)
  • Re: Faithful Ancestors was Re: Doesnt ANYONE have anything new to say?
    ... about sexual dimorphism in A. afarensis and how Owen Lovejoy is the smartest person in the field because he said what I've been saying for years that the dimorphism is wildly over estimated in a self fulfilling prophecy of assuming big bones are male and small bones female. ... "Finally, cursed with a scarcity of pelvic remains that could clearly distinguish wider-hipped females from slimmer-hipped males, McHenry simply assumed that big bones came from males and small bones came from ... If McHenry found their bones after a few million years of wear and tear, he would declare the big bones male and the little ones female. ...
    (sci.anthropology.paleo)
  • Re: Faithful Ancestors was Re: Doesnt ANYONE have anything new to say?
    ... the key point is that male size equals reproductive ... Humans & chimps exhibit less dimorphism, ... have less success at monoplising access to females (with differing ... the big bones as male and the little bones as female. ...
    (sci.anthropology.paleo)
  • Re: blue betta
    ... any problems (like male attitude) with them between eachother? ... I've had many females hold ... I've had females that would kill any male put into their tank. ... female can (although not in my hard water) get as large as a male, ...
    (rec.aquaria.freshwater.misc)
  • Re: Male Monkeys That Pay for Sex
    ... Do Monkeys Pay for Sex? ... researchers found that male primates "paid" for sexual access to females ... available females went up. ... about 50 long-tailed macaques in Kalimantan Tengah, Indonesia, traded ...
    (talk.origins)