Welcome again. This is part two of my talk
on "Dental Morphology: Anthropological and Forensic Applications".
And now that we've covered the basics and gone over
the pattern variation of crown and root traits throughout the world,
now we're going to address
the evolutionary mechanisms that underlie variation in dental morphology,
and also talk about
anthropological and forensic applications
of tooth morphology in bioarchaeology in forensic anthropology.
Now, several questions pop up.
The first thing we're going to address
is why do we see this variation in dental morphology?
How is this impacted by the various evolutionary mechanisms?
We're going to ignore mutation because mutation is very rare
and we have no traits that we could actually link to a mutation,
not counting rare enamel defects and things of that nature.
I'm just talking about the morphological traits that we've been discussing.
So, we'll consider natural selection,
sexual selection and then address the role of genetic drift and founder effect,
and finally, gene flow,
all in the context of these dental morphological traits.
Okay, for a long time individuals thought that there must be
some direct selection impacting these traits and
the basic argument was that if a trait added to crown surface,
it would prolong the life of the tooth and that would contribute to
the differential survival and maybe fertility of the bearer of those traits.
And so, the traits,
most often addressed in that context,
were Carabelli cusp and shovel-shaped incisors,
and some even suspect the three-rooted lower first molars
might, you know, anchor the tooth in the socket for
a longer period of time and then enhance tooth longevity.
So, although that sounds good in principle,
it's extremely difficult to prove or demonstrate in practice.
So, more recently, there are indications that some of
these traits may be subject to indirect selection and for example,
if a trait like shoveling is linked to alleles that are more closely tied
to adaptation and there are interesting terms associated with this notion,
genetic hitchhiking or genetic draft,
where the selection does impact the trait.
But it's not impacting it directly but rather indirectly.
And one of the most exciting developments in the last decade is showing that
the EDAR 370A alleles that affect variables of skin,
hair and teeth also affect morphological traits including
shoveling and molar cusp numbers.
So, this may explain quite a bit
about those shoveling distribution I illustrated a few slides back.
So, we're still working on this,
but it's a very very interesting and promising area.
Although, we're not sure how far this will go in terms of selection.