More on human-orangutan analysis

[John grehan]

At 02:56 PM 6/25/2003 -0500, Will Fischer wrote:
>There are some points missing from John Grehan's recent post:
>
>1. The analysis of craniodental characters by Collard and Wood(*)
>doesn't strongly support a Homo-Pongo clade: the most parsimonious tree
>for the full dataset was (Hylobates,(Homo,(Pan,(Gorilla,Pongo)))) --
>the (Homo,Pongo) clade was from a bootstrap consensus tree only.

This does not change the fact that they rejected the tree because it did
not agree with the molecular tree. On p. 5004 (bottom of last paragraph)
they refer to the analysis as a parsimony analysis not a bootstrap
analysis. But apparently I've misunderstood.

>2.  Regardless of the conclusions of the paper, the point to the
>exercise (which Dr. Grehan apparently doesn't recognize) is to identify
>the discrepancy between the craniodental characters and the molecular
>characters -- one of the data sets must be giving the wrong answer
>(which one, of course, remaining an open question).

Of course I recognize the point and I'm at a bit of a loss to understand
why my statements were seen to indicate otherwise, but then I wrote what I
wrote and must take the criticism of my ineffective writing.

However, as to which data set giving a wrong answer being an open question
is not the case for these authors. To them it is not an open question as
the molecular data is taken to be right.

>3.  However, and finally, the analyses of soft tissue characters (both
>in 2000(+) and 2002(++)) got the same tree as the molecular data.

Agreed. This does not change the fact that they got a different answer in
the paper to which I referred.

>If a majority of the morphological characters supported a Homo-Pongo
>clade, you could make an argument for it.  Since the hard-tissue data
>are ambiguous, while the soft-tissue data and the molecular data are
>congruent, it's hard to be enthusiastic about the unconventional
>hypothesis, or your advocacy for it.

The problem here is that these analyses do not include the full suite of
Homo-Pongo apomorphies available. However, its a good enough point and
there are two issues that are under consideration. The first is what
happens when the orangutan characters are added, and what happens when
characters are removed from the original analysis because they are
incorrectly treated as apomorphies. I am looking into both currently. With
the Shoshani et al paper, for example, there are at least 15 characters
that do not stand up (even the source cited for some characters do not say
what they are supposed to).

>Since this all started in the context of a museum exhibit, why not
>present (a BALANCED selection of) all the data:  sections of sequence
>alignment (with differences highlighted), and a series of pictures of
>hard- and soft-tissue character states.  Get the folks who attend the
>exhibit to map the character states on the trees;  if you provide
>"answers", make them be of the form:

I like the suggestion although it would not work for the kind of exhibit
space we have (we are a very small museum) and much of the audience is
driven by families with younger children. However, there are possibilities
for the web page and I will keep the suggestion in mind. In principle,
however, there are aspects that may be presented in a more descriptive form
for the exhibit.

>characters group on some of them, and then you can get folks thinking
>about what evolutionary forces might cause some characters to converge.

This is also a pretty big area and in the given space I cannot cover
aspects of molecular drive and other genetic turnover mechanisms that might
be involved, not to mention unknown environmental influences (if they did
have a role).

>  For it to be fair, though (and other people on the list have mentioned
>it), you'll have to choose the characters on display proportionally
>according to the tree they support.

The display will focus on the fact that there are two different models. It
will present the key elements of evidence as much as possible in a small
space with a given audience in mind. No doubt it will be less than
satisfactory in many respects. The web page may help and I will get input
on the genetic side (already had some of that from molecular people). The
exhibit will also feature a new illustration of Lucy to be compared with
our traditional picture as a focal point for comparison (for the
interesting issue is if chimps are our nearest relative why do
australopithicenes have a skull with the face shaped like that of an
orangutan, and teeth like an orangutan etc. (i.e nothing like a chimp).

John Grehan