The aardvark or "earth pig" may be the closest living relative to the ancestral placental mammal, a new chromosomal comparison suggests. Molecular sequence analyses group it with tenrecs, hyraxes, elephant shrews, manatees, elephants, and golden moles as "Afrotheria," the oldest of four groups of placental mammals that originated, according to fossil evidence, on the supercontinent Gondwana 105 million years ago.
Terry Robinson, professor of zoology at the University of Stellenbosch in South Africa, and colleagues used fluorescence in situ hybridization (FISH) to compare chromosomes of aardvarks, humans, and elephants (F. Yang et al., "Reciprocal chromosome painting between human, aardvark, and elephant (superorder Afrotheria) reveals the likely eutherian ancestral karyotype," Proc Natl Acad Sci, 100:1062-6, Feb. 4, 2003). They found that every human chromosome (except the Y) has an aardvark counterpart, with some segments fused and others split over time. "Chromosomes are often rearranged during the course of evolution. But the ...
