Sizing-up the brain.
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Body Constitution↗
Biomedical subjects
L M Van Valen
Publications and source records attributed to L M Van Valen.
Homology and causes.
Homology is resemblance caused by a continuity of information. In biology it is a unified developmental phenomenon. Homologies among and within individuals intergrade in several ways, so historical homology cannot be separated sharply from repetitive homology. Nevertheless, the consequences of historical and repetitive homologies can be mutually contradictory. A detailed discussion of the rise and fall of the "premolar-analogy" theory of homologies of mammalian molar-tooth cusps exemplifies such a contradiction. All other hypotheses of historical homology which are based on repetitive homology, such as the foliar theory of the flower considered phyletically, are suspect.
Anatomy, Comparative↗
The archaebacteria and eukaryotic origins.
Critical analysis of the phylogeny of prokaryotes is in its infancy. Woese and others have made the startling proposal that methane-producing bacteria and a few others form a phyletically unified group, the Archaebacteria, as old and as diverse (although not now as numerous) as all other bacteria. The only critique of this proposal is inadequate. Here we present an alternative view, that the Archaebacteria were derived from other bacteria and contain the ancestor of a cell which engulfed others, eventually to become the first eukaryote.
Archaea↗