Casey Luskin has a misleading piece about Selam – the juvenile Australopithecus afarensis specimen that has been in the news recently. The Luskin piece is over at Evolution News and Views – the propaganda arm for the DI. Lets take a look at how accurate Luskin is…
An exciting find was recently reported as scientists discovered what may be the most complete australopithecine fossil specimen ever found. It is reported to be a toddler. Unfortunately, the media is misrepresenting this fossil as if it closely mimics humans. Consider the diagram below which comes from the Seattle Times (“Scientists Find Fossil Child from 3.3 Million Years Ago,” Thursday Sept. 21, 2006, pg. A2):
Does Australopithecus afarensis really look so similar to humans? This diagram is extremely misleading. Consider a diagram from an actual scientific paper which reveals the stark differences between Australopithecus (right) and the earliest members of our genus, Homo (left):
Okay, let’s look at the pictures. Here is the picture that has Luskin so upset, it comes from an article in the Seattle Times
If you look down at the bottom left hand corner you will note that it says “Sources:Nature, 2004;Laszlo Meszoly”
The picture in question came from a scientific paper in Nature. The paper is: Endurance running and the evolution of Homo, Dennis M. Bramble, Daniel E. Lieberman Nature 432, 345 – 352 (18 Nov 2004) so Casey is the person being misleading here, not the media. Casey makes a deeper error. Note the circled parts of the picture along with the accompanying explanations of what the circled areas represent:
“Organ of balance in inner ear more ape like than human”, “New partial fossil evidence of the Australopithecus afarensis suggests an apelike anatomy better at climbing than humans”, etc. I offer a explanation below for how Luskin missed this, incredibly obvious as it is to anyone who bothered to read the article or look at the picture. Which perfectly illustrates some comments in the article:
The remains also confirm how much of a hybrid between humans and apes these creatures were. While they had legs like humans that enabled them to walk upright on two feet, they had shoulders like gorillas that may have also enabled them to climb trees. While their teeth seem to have grown quickly, like chimps’ teeth, their brains may have matured more slowly, like humans.
“This confirms the idea that human evolution was not some straight line going from ape to human,” said Rick Potts of the Smithsonian Institution. “The more we discover, the more we realize that different parts evolve at different times, and some of these experiments of early evolution had a combination of humanlike and apelike features.”
Really, the only thing Luskin can legitimately object to is the size of the two figures…
Lets look at the picture Casey likes, which has a smaller australopithecine:
It comes from an article published in January, 2000 in Molecular Biology and Evolution and was written by Hawks, Hunley, Lee and Wolpoff (Casey proceeds to quote mine the hell out of the article and the accompanying press release). Casey says:
The media is calling this baby fossil “a mixture of ape-like and human-like features,” yet that description obscures the real picture. A recent study in the Journal of Molecular Biology and Evolution found that Homo and Australopithecus differ dramatically:
We, like many others, interpret the anatomical evidence to show that early H. sapiens [H. erectus and H. ergaster] was significantly and dramatically different from … australopithecines in virtually every element of its skeleton and every remnant of its behavior.
(J. Hawks et. al, “Population Bottlenecks and Pleistocene Evolution,” Journal of Molecular Biology and Evolution, 17(1):2-22 (2000).)
It goes without saying that a paper published six years ago can hardly be considered recent. Lets look at what Alemseged et al 2006 – the paper that announced the discovery of Selam – has to say:
Postcranium of DIK-1-1. Most bipedal features seen in A. afarensis
specimens are observed on the lower limband foot of DIK-1-1…
Overall, the tibiae–with their transversely expanded shaft beneath
the tibial plateau–are similar to that of the juvenile A.L. 333-39
…, but have a sharper anterior border also shown by modern
humans (Fig. 2b). As in modern humans, the tibialis anterior muscle
originated anterior to the interosseous ridge and occupied the lateral
side of the tibial shaft, extending the sharp anterior border. The
tibialis posterior muscle occupied the lateral aspect of the posterior
part of the shaft. Similar to humans, the lateral upper part of the shaft
is rather concave, particularly just below the condyles, and becomes
convex more distally. Also, the cross-section of the shaft changes
from triangular proximally to oval at its distal-most preserved part.
The bicondylar angle and symmetrical condyles are additional
features previously known in A. afarensis. The medial and lateral
borders of the talar trochlea are similar in curvature and height
(Fig. 2d), and the partly exposed medial side of the talar body is
vertical in surface orientation (Fig. 2d). The calcaneus of DIK-1-1 is
robust, as in humans, and its distal part is mediolaterally wider in
relation to its dorsoplantar dimension compared with that of Pan.
Later in the paper Alemseged et al state:
The DIK-1-1 skeleton confirms the functional dichotomy of the
body plan of A. afarensis: a more derived lower body adapted for
bipedal locomotion, combined with an upper body that is, in many
respects, ape-like. The functional interpretation of these features is
highly debated, with some arguing that the upper limb features are
non-functional retentions from a common ancestor only…,
whereas others propose that they were preserved because A. afarensis
maintained, to some degree, an arboreal component in its locomotor
repertoire… Now that the scapula of this species can be examined
in full for the first time, it is unexpected to find the strongest
similarities with Gorilla, an animal in which weight-bearing and
terrestrial knuckle-walking predominately characterize locomotor
use of the forelimbs… Problematic in the interpretation of these
findings is that the diversity of scapula architecture among hominoid
species is poorly understood from a functional perspective.
I’ll get back to the scapula in a bit. So their seems to be some inconsistency between the two at least if one reads no further into Hawks et al 2000. Later in the article they state:
If we assume these earlier australopithecines are a
group of very closely related species, for instance, nearer
to each other than Pan and Homo, we can expect that
they differ much more in allele frequencies than in the
presence or absence of specific genes for these features.
Therefore, a reshuffling of existing alleles could result
in the frequencies of features we observe in early H.
sapiens. Thus, our second question is about this reshuffling,
whether early H. sapiens is a consequence of rapid
speciation with significant founder effect or the result of
a long, gradual process of anagenic change. The first
explanation, cladogenesis, is suggested by the fact that
no gradual series of changes in earlier australopithecine
populations clearly leads to the new species, and no australopithecine
species is obviously transitional. This may
seem to be an unexpected statement, because for 3 decades
habiline species have been interpreted as being
just such transitional taxa, linking Australopithecus
through the habilines to later Homo species. But with a
few exceptions, the known habiline specimens are now
recognized to be less than 2 Myr old (Feibel, Brown,
and McDougall 1989) and therefore are too recent to be
transitional forms leading to H. sapiens.
Our interpretation is that the changes are sudden and
interrelated and reflect a bottleneck that was created because
of the isolation of a small group from a parent
australopithecine species.[emphasis mine and added later – afarensis – this just goes to show how wrong Casey is, Hawks et al clearly think australopithicines are ancestral to later human species they are just disputing the mechanism and whether the habilines are ancestral to later homo]
In this small population, a combination
of drift and selection resulted in a radical transformation
of allele frequencies, fundamentally shifting
the adaptive complex (Wright 1942); in other words, a
genetic revolution (Mayr 1954; Templeton 1980).
Whereas Alemseged et al 2006 approached A. afarensis from the standpoint of mosaic evolution (and anagenesis), Hawks et al 2000 approach the issue from the standpoint of population genetics leavened with cladistics (and punk eq). I don’t think Hawks, for example, would disagree with the way Alemseged characterized the postcrania of DIK-1-1 – but he can speak for himself on that issue. Which brings us back to the scapula which has been compared to the scapula of a gorilla – based on measurements of the scapula. Below is a picture of four scapulas – all juvenile. Top left: DIK-1-1. Top right: Gorilla. Bottom left: Human. Bottom right: Chimp
Of the four the chimp scapula stands out as being the most noticeably different (at least to me). Interesting, no?
Finally, Casey finishes off whining with the following:
This new baby Australopithecine find is surely exciting and will expand our knowledge of the extinct genus of Australopithecine apes (Australopithecus literally means “Southern Ape”). But don’t let misleading diagrams in the media make you think that these apes were clear-cut similar ancestors of our genus Homo.
Well, the name Orangutan means “Old Man of the Woods” so following Casey’s logic all orangs are really old (male) humans that live in the woods (even the babies)…