Molecular
phylogeny of Homo and other Primates
(based on coding regions of the
mtDNA genome)
All members of the order Primata are characterized by a distinctive skull feature, a complete bony ring around the eye orbits that facilitates binocular vision. The diagram shows the relationships of modern and extinct species of Homo to other living primates, as inferred from the complete protein-coding regions (~ 15 Kbp) of the mitochondrial DNA (mtDNA) genome.
The evolutionary tree shows the evolutionary relationships of
humans relative to the
other Great Apes, the
Great Apes relative to the Lesser
Apes, Apes relative to the Old World Monkeys, the
separation of Old and New World
Monkeys, and the relationships of "monkey-like"
primates to Pro-Simian tarsiers. Another pro-simian
group is the Lemurs (not shown).
In
such trees, degree of evolutionary relationship is
determined by tracing the branching order back
to the Most Recent Common Ancestor (MRCA) of
any group relative to another. Organisms that share a more
recent MRCA are more closely related. Degree of
evolutionary similarity is determined by
counting the number of base changes (Single
Nucleotide Polymorphisms, SNPs) along the
branches connecting any two species. Among the
Great Apes, humans (Homo) are more closely related
to chimps (Pan) than either is to gorillas (Gorilla)
or to orang-utans (Pongo). It also shows that extinct
and modern human species are far more similar to
each other than are different species of chimps, gorillas,
or orang-utans.
Homework: Prior to the
advent of molecular data in the 1960s, it was assumed that
the large organismal differences between Humans relative to
the Great Apes was due to a large amount of genetic change
along the human lineage. Test this hypothesis by counting
& recording the number of SNP changes
between the six pairwise combinations of Homo sapiens,
Pan troglodytes, Gorilla gorilla, and Pongo
pygmaeus. (1) What is the expected result if the old
hypothesis is correct? Do the
data support or reject the hypothesis? Explain.
(2) Do the data support or reject the hypothesis that
morphologically similar chimps and gorillas are also
genetically similar to each other? Explain
Analysis & text
material © 2022 by Steven M.
Carr