Sorry for the late input. I had finals....
Originally posted by Heronumber0
Byrd, thanks for the anatomy input here. I was trying to make sense of what Filler was saying but found it too technical to handle.
Some of that was rather deliberate obfustication on his part -- or bad writing. Poorly mixed metaphors like this one "
The next three chapters
(4-6) reveal a tectonic change in our understanding of the mechanisms and methods by which important changes take place in evolution certainly
don't make it any more readable.
...spine essentially incompetent for routine quadrupedal
locomotion.
That's a rather sweeping statement for him to make with only a sacrum and a vertebra and not the rest of the skeleton. I notice that his redrawn
claidagram doesn't actually place Morotopithecus anywhere on the scale.
www.uprightape.net...
...and his comparative anatomy drawings of the sacrum don't include the Morotopithecus sacrum... and they're only drawn one half and from the back.
That's sort of a cheat, because when you draw them from the side, the human sacrum has a curve in it that the chimp and gorilla and apes don't have.
Scroll down to "figure 4" in this PDF and you'll see what I mean... ape sacrums are quite straight, like that fossil:
cmpd.umd.edu...
And while he calls gibbons bipedal, the truth is that they spend very little time walking on two feet and they sway lots while doing it.
The lack of any intrinsic mechanism to
resist extension under the force of gravity in a horizontal
pronograde position allowed the lumbar spines of these
apes to function well only in upright or orthograde postures.
The large modern hominiform apes such as gorillas
and orangutans have independently evolved new types of
osseous ridges that lock the lumbar facets against extension.
Here, he's talking about how the vertebra sort of 'lock' into place to allow or restrict flexibility. There's a number of ways that nature
evolves this (including, in dinosaurs, long ribs that run down along the neck vertebra and thick tendons that run along the tail vertebrae.)
This finding suggests a continuous series of upright
ancestral apes—with body plans more or less like those in
a modern human—from which other apes have descended
to establish diagonograde (between upright and horizontal)
postures during knuckle walking and other straightarm/
flexed-leg gaits.
According to others, it suggests that human-ape ancestors had more flexible spines. This is not surprising, given that they were much smaller animals
and a flexible spine gives more 'spring' to the leap.
He seems pretty convinced, if I read this properly, that we had an upright ape which was not capable of bending down like a normal ape. I would see
that as a stronger survival feature (from a neo-Darwinian point of view) than a partially upright ape.
I take the point about the fossil record showing loss of features in gradation for example horses getting smaller etc.. but is the fossil
record for human/hominids really that complete?
Nowhere near as complete as we'd like... and we'd like to see fossils from all areas of the globe. It's reasonably good for Australopithecus on
upwards, but further back there's fewer hominid fossils.
My theory is that hominids were considered tasty, catchable dinners by almost every predator around.
Doesn't the process go through long periods of stasis followed by short periods of rapid change? The punctuated equilibrium theory seems
pretty convincing in this regard.
It is if you look at selected material. In other cases, the changes take place over a long period of time (and may show up in the form of 'zillions
of different species of this kind of critter.' In the Cretaceous, the ceratopsian dinosaurs evolved to many different species (including
torosaurus), and we're still finding new ones (my boss is working on some material that may be a new one, and I worked on a horn frill 2 years ago
that seemed to come from an unknown ceratopsian species.
