Chris Colby
Herb Huston
Brett J. Vickers

HH> There's a minority view that holds that the division of pongids
HH> and hominids is unjustifiable based on findings in molecular
HH> biology.  These folks would group chimps, bonobos, and us
HH> (and possibly gorillas) together leaving the orang as odd ape
HH> out.

CC> "It is (IMHO) ridiculous to put humans in a separate family when
CC> we are more genetically similar to chimps than many sister
CC> species are to each other. Pongids are (in the current
CC> classification) a paraphyletic clade; e.g. species derived
CC> from others within the clade are excluded.

CC> orangutan     gorilla         chimp   human
CC>  |              |               |       |
CC>    \                \               \   /
CC>        \               \              |
CC>            \              \         /
CC>                \             \  /
CC>                   \           |
CC>                       \    /
CC>                          |
CC>
CC> To me it doesn't make sense to have a group consisting of
CC> gorillas and chimps, but not humans. (The same could be
CC> said for reptiles and fish, incidentally -- these groups
CC> are also paraphyletic.)


BJV> "The traditional phylogenetic reconstruction looks like this:

BJV> orangutan     human           chimp   gorilla
BJV>  |              |               |       |
BJV>    \                \               \   /
BJV>        \               \              |
BJV>            \              \         /
BJV>                \             \  /
BJV>                   \           |
BJV>                       \    /
BJV>                          |
BJV>
BJV> but (as you prove) there is a dispute as to which phylogeny is more
BJV> accurate.  Some studies and data suggest that your phylogeny
BJV> is the best, but others suggest the traditional one.
BJV>
BJV>       "Some tentative chromosomal data have suggested that
BJV>        humans and chimps share a more recent ancestry after
BJV>        separating from gorillas (Yunis and Prakash, 1982).
BJV>        A more controlled study, however, with consideration
BJV>        of within-species variation of karyotype (Stanyon and
BJV>        Chiarelli, 1982), has supported the more traditional
BJV>        branching order, where humans and both African apes
BJV>        diverge first -- followed later by a separation of
BJV>        chimps and gorillas." [1]
BJV>
BJV> The following amino acid, antigenic and DNA distances are reported
BJV> here just because I find them interesting:
BJV>
BJV>                               Amino Acid      Antigenic       DNA
BJV>                               Distance        Distance        Distance
BJV>                               ------------    ------------    -----------
BJV> Human--chimp                  0.27            1.0             1.8
BJV> Human--gorilla                        0.65            0.8             2.3
BJV> Human--orang                  2.78            2.0             4.9
BJV> Human--gibbon                 2.38            2.6             4.9
BJV> Human--macaque                        3.89            3.6             --
BJV> Human--spider monkey          8.69            7.6             --
BJV> Human--tarsier                        --              8.8             --
BJV> Human--loris                  11.36           11.2            42.0
BJV> Human--tree shrew             --              12.6            --
BJV> Primates--other placentals    --              12.11-14.91     --
BJV> Placentals--marsupials                --              15.83           --
BJV>
BJV> The numbers listed above are unitless.  The scales are relative.
BJV>
BJV> If you buy the hotly contested molecular clock theory that antigenic
BJV> distance determines phylogenetic branching dates, then you can pick the
BJV> branching dates out of the data above.  I have to admit I'm a little
BJV> partial toward the theory because one of my anthropology professors had
BJV> Vincent Sarich as his advisor.

BJV> Some people believe chimps and humans should belong to the same genus.
BJV> That way we'd have Homo sapiens and Homo troglodytes [1].  I think the
BJV> only reason that we don't is because humans like to think they're special.
BJV>
BJV> [1] H. Nelson, R. Jurmain, _Introduction to Physical Anthropology_,
BJV>     4th edition, West Publishing Co., St. Paul, 1988.