The big news in the world of paleoanthropology this week was the publishing in Science (340:163-5) of six articles specifying aspects of the two million year old hominid, Australopithecus sediba, found in South Africa in 2008. Studies of this hominid, who lived after our own Homo genus appeared about 2.4 million years ago, show a typical “mosaic” pattern. The upper limbs are ape-like; the upper part of the rib cage is ape-like and the lower more human-like; the spine is human-like; the feet are in between; and the teeth are a virtual grab-bag of dental land marks along the early ape-us path.
Let’s step back and consider early hominid evolution in the larger context of the evolution of the other two members of the “hominin” family, into which we have been shamelessly demoted by some anonymous taxonomists to be in the same pigeon-hole as gorillas and chimpanzees (if you are interested in the politics of this decision, click this). No fossils from the last six million years have been found of them because they have basically been “refuge” species all along. Apes were going out of business when hominids showed up. So why did we all of a sudden explode into 18 different species and counting, all basically headed in the same direction with various body parts evolving at different speeds, which is what mosaic evolution is. The point is that it doesn’t matter a whit which is descended from which. What is so striking is that they are ALL going FROM BEING APE-LIKE TO BEING HUMAN-LIKE. How could anyone think that this direction was an adaptation to the climate in Africa at that time?
“Externalism takes selection as the main force producing pattern…Internalism gives form primacy over function…Consider how the two schools would approach the problem of evolving an angel:
If an angel is all that you lack
Take a girl with small blips on her back.
The genes that she brings
Will soon program for wings
So selection’s the line of attack.
If your aim is an angel who sings
And flies with her elegant wings
You’ll not do it by means
Of dicing with genes.
New generative rules are the things.”*
As those of you that have been following this blog know, I like God’s answer. An internal evolutionary innovation in the mental and emotional sphere triggered the hominid radiation, which amounted to the creation of “new generative rules.” These new rules were those of right and wrong such that small monogamous groups evolved to coordinate their behavior as single organisms. Want to read about this evolutionary revolution? Read this.
*SJ Arnold, et al (1989) How do complex organisms evolve?:405