The New York Times has an article up reiterating the fabled “bushiness” of hominid phylogenetic trees:
Scientists who dated and analyzed the specimens — a 1.44 million-year-old Homo habilis and a 1.55 million-year-old Homo erectus — said their findings challenged the conventional view that these species evolved one after the other. Instead, they apparently lived side by side in eastern Africa for almost half a million years.
My knowledge of bones is not strong, so I leave it to John Hawks or Kambiz to decompose the details. That being said, the big picture is that this is another strike against anagenesis for the human lineage, which basically is a scientific concept expressed in the famous t-shirts showing a progression from ape to ape-man to Neandertal to modern human. Anagenesis easily slots into human cognitive biases such as the “Chain of Being,” and I don’t know how revolutionary it is to bury it again for the thousandth time. All that being said, it is a little irritating to see this bit of pop-evolutionary thinking crop up near the end of the piece:
Susan Anton, an anthropologist at New York University and one of the report’s authors, said that the small skull pointed up a significant variation in the sizes of erectus specimens, particularly differences between the male and female of the species, or sexual dimorphism.
Such a characteristic is thought to be a primitive stage in evolution. In humans, males average about 15 percent larger than females, and the same is true for chimpanzees. Sexual dimorphism is much more striking in gorillas, and apparently also in erectus.
1) If you are writing about evolution you had best be cautious about throwing out the term “primitive.” Ancestral and derived would be more precise and less loaded, if a bit more opaque to less verbally fluent readers.
2) Sexual dimorphism isn’t “primitive” in any case. Just as chimpanzees and gorillas are no more “primitive” than human beings. Man is not the measure of evolution. Additionally, gibbons have very little sexual dimorphism, and if man was the measure of a beast then they would be far more primitive than gorillas or chimpanzees.