Serological tests reveal evolutionary relationships

Early in the twentieth century scientists studied blood immunity and how immune reaction could be used to compare species. The blood studies tended to produce results that parallel the more obvious indicators such as body plan. For example, humans were found to be more closely related to apes than to fish or rabbits. These findings were said to be strong confirmations of evolution. In 1923 H. H. Lane cited this evidence as supporting “the fact of evolution.” (Lane, 47) Later in the century these findings continued to be cited in support of evolution. (Berra, 19; Dodson and Dodson, 65)
 
But even by mid century contradictions to evolutionary expectations were becoming obvious in serological tests. As J.B.S.Haldane explained in 1949, “Now every species of mammal and bird so far investigated has shown quite a surprising biochemical diversity by serological tests. The antigens concerned seem to be proteins to which polysaccharides are attached.” (quoted in Gagneux and Varki)
 
Indeed these polysaccharides, or glycans, did not fulfill evolutionary expectations. As one paper explained, glycans show “remarkably discontinuous distribution across evolutionary lineages,” for they “occur in a discontinuous and puzzling distribution across evolutionary lineages.” (Bishop and Gagneux) These glycans can be (i) specific to a particular lineage, (i) similar in very distant lineages, (iii) and conspicuously absent from very restricted taxa only.
 
Here is how another paper described glycan findings: “There is also no clear explanation for the extreme complexity and diversity of glycans that can be found on a given glycoconjugate or cell type. Based on the limited information available about the scope and distribution of this diversity among taxonomic groups, it is difficult to see clear trends or patterns consistent with different evolutionary lineages.” (Gagneux and Varki)
 
References
 
Berra, Tim. 1990. Evolution and the Myth of Creationism. Stanford: Stanford University Press.
 
Bishop J., P. Gagneux. 2007. “Evolution of carbohydrate antigens--microbial forces shaping host glycomes?.” Glycobiology 17:23R-34R.
 
Dodson, Edward, Peter Dodson. 1976. Evolution: Process and Product. New York: D. Van Nostrand Company.
 
Gagneux, P., A. Varki. 1999. “Evolutionary considerations in relating oligosaccharide diversity to biological function.” Glycobiology 9:747-755.

Lane, H. 1923. Evolution and Christian Faith. Princeton: Princeton University Press.