Does Darwinian evolution acting over a sufficiently long period of time really offer a complete explanation, or are unusual genetic events and particular environmental and ecological circumstances also involved? With The Origin of Higher Taxa, Tom Kemp sifts through the layers of paleobiological, genetic, and ecological evidence on a quest to answer this essential, game-changing question of biology. More.
A legitimate response would be: Do you still need your job, Kemp? If so, you know that the answer is Yes. (Turns out he doesn’t still need his job, so … )
We are told,
Kemp here offers a timely and original reinterpretation of how higher taxa such as arthropods, mollusks, mammals, birds, and whales evolved—a bold new take on the history of life.
But what new take exactly?
His page tells us,
My broad field is vertebrate palaeobiology, and I am particularly interested in the mammal-like reptiles and early mammals, and what can be inferred about the structural, functional and ecological aspects of the origin of mammals from their basal amniote ancestry. I also use this case as a paradigm for thinking about major evolutionary transitions and the origin of new higher taxa in general: how long treks through morphospace, involving substantial changes in many characters over the geological time scale, can occur while the phenotype necessarily remains a highly complex, well-integrated entity. I am exploring the extent to which this evolvability versus integration paradox at the phenotypic level can be resolved by the correlated progression model of evolution, and am also concerned about the nature of the adaptive landscapes across which such enormously long-term trends can travel
Here’s the abstract of a 2007 paper:
The origin of a new higher taxon is characterized by a long-term phylogenetic trend, involving evolutionary changes in a large number of characters. At this phylogenetic level, the conflict between internal integration of the phenotype and its evolvability can be resolved by the correlated progression model, in which many disparate traits evolve by a sequence of small increments in loose correlation with one another, rather than by the modularity model. The trend leading to the new higher taxon implies the existence of a long ridge in an adaptive landscape. An evolutionary lineage tracking it requires adaptive changes in broad biological characteristics, involving many traits. Species selection is a possible additional driver of the trend. These conclusions are tested against the synapsid fossil record of the origin of mammals. The reconstructed sequence of acquisition of mammalian traits supports the correlated progression model. The adaptive ridge involved is postulated to have been a sequence of overlapping niches requiring increasing ability to remain active in daily and seasonally fluctuating environments by means of increasing internal regulation. An inferred speciation bias in favour of relatively small, relatively more progressive carnivores indicates that species selection was also involved in driving the trend. Palaeoenvironmental evidence indicates that ecological opportunity probably played a role at certain points along the lineage. (paywall)
T. S. Kemp is an emeritus university lecturer and curator of the zoological collections in the Department of Zoology at the University of Oxford. He was also a tutor in biology for St John’s College, where he now holds an emeritus research fellowship. He is the author of Mammal-Like Reptiles and the Origin of Mammals, Fossils and Evolution, and The Origin and Evolution of Mammals.
Did he manage to get away in time without really saying anything?
See also: What the fossils told us in their own words
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Hat tip: Pos-Darwinista