Hominoid cytogenetics and evolution

Abstract

Much of the literature on the chromosomes of the Hominoidea exists in virtual isolation from both evolutionary theory and physical anthropology. Several unjustified speculations about hominoid affinities in the literature of cytogenetics may be attributed to the effects of this isolation. In this paper, the literature of comparative hominoid cytogenetics is reviewed, and that on chromosomal band patterns and repetitive DNA distributions relative to current evolutionary theory is discussed. These data are critically analyzed and shown to be more consistent with an orthodox hominoid phylogeny than with heterodox phylogenies. Rates and modes of karyotypic evolution are also discussed in an attempt to begin to assimilate the study of hominoid chromosomes within the framework of physical anthropology.The study of the the cytogenetics of primates has generated an enormous amount of information, which has not yet been assimilated into the main fabric of physical anthropology. The reasons are several: (1) The work has appeared in specialized cytogenetics journals; (2) the work has been done by researchers unfamiliar with the discipline of physical anthropology; (3)the interpretations do not have a coherent phylogenetic framework, and have produced heterodox conclusions; and (4) primate cytogenetics is frequently compromised by an unfamiliarity with the lingua franca of comparative life-science, the systematics of the animals being studied. This last point is important as the lack of facility with primate taxonomy undermines the researchers' credibility and obscures the meaning of comparative statements (Table 1).This review attempts to take what has been learned about the organization of the genetic material of the primate superfamily Hominoidea and to fit it within the generally accepted framework of catarrhine evolution. It also criticizes some of the existing interpretations of the cytogenetic data. The review is divided into five sections: (1) a discussion of the history and significance of hominoid chromosomes; (2) chromosomal banding homologies of the great apes and humans; (3) repetitive DNA sequences in these primates; (4) variation in rates of chromosomal evolution; and (5) a discussion of phylogenetic inference based upon chromosomal data.The following general evolutionary tenet is adopted for this review: Phylogenetic sister groups, closest relatives, are to be recognized by the sharing of derived traits, evolutionary novelties, not by the sharing of ancestral traits (Hennig, 1965;Simpson, 1975). The useful, if cumbersome, Hennigian lexicon is adopted to highlight this distinction.Finally, there is a subtle, but critical, difference between cytogeneticists and evolutionary biologists in use of the term «homology." In cytogenetics, homology is taken as phenetic similarity of chromosomes antecedent to phylogenetic reconstruction (the word "homoeology" refers to less phenetic similarity). Thus, Prakash (1982 p. 1529) write that «no homology could be found" among the Ychromosomes of the apes before the...

A Comparison of the Karyotypes of Six Species of the Genus Macaca and a Species of the Genus Cercocebus

“…It has been proposed that the socioecology of primate species determines their rate of chromosome evolution [Wilson et al, 1974Marks, 1983], Socioecology deter mines the effective population size which in fluences the rate of chromosome evolution. Lande [1984] has shown mathematically that given a constant rate of chromosomal change, new chromosome aberrations have a very low chance of becoming fixed in a pop ulation unless the effective population size of the breeding units of a species is fairly low.…”

Assignement of the fibronectin (FN1) gene to pongo pygmaeus (Organgutan) chromosome 11

“…Comparative gene mapping data reported from two groups (Marks, 1983 andLalley et al, 1989) turned out to be contradictory with respect to each other and with the cytogenetic data. As a result, we have focused our interest on mapping in great apes further genes which have already been localized on human chromosome 2.…”

Evolutionary divergence of the oncogenes GLI, HST and INT2

“…These chromosomal modifications in PTR 10 and GGO 10 may have occurred at a common trunk for PTR and GGO, after the event when populational evolution occurred, at the end of a common trunk for HSA, PTR and GGO (Dutrillaux & Rumpler, 1988). Ribosomal DNA studies may also provide evidence that PTR and GGO shared an exclusive common trunk (Marks, 1983). However, if this is not the case, then explanations may include a potential back-mutation in HSA 12 or a possible polymorphism for the two states of chromosome 12 in the GGO/PTR/HSA ancestor continuing to the PTR/HSA ancestor, with subsequent fixation of alternate states in GGO and PTR (in one respect) and humans (in the other).…”