Forensic Archaeology and Anthropology - Part.1: Sexing a Skeleton (Final Edit)

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Once you have your
skeleton in the lab

and you've laid it out
in anatomical position

and you've recorded all
the bones that are present,

the first aspect of identity
that you want to establish

is sex.

One of the reasons
that you do this first,

is because some of the other
techniques are sex-dependent.

Now we only sex the skeletal
remains of adult individuals.

This is because establishing
sex of non-adults

has been shown to be unreliable.

There are a number of techniques
that have been developed,

but when they've been applied
to different populations,

their reliability
is not so strong.

Part of the reason for this
is that sexual dimorphism.

So the differences
between males and females

does vary slightly between
different populations.

So this can be
confusing if you're

dealing with juvenile remains.

So today, we're just going
to focus on establishing

the sex of adult skeletons.

The pelvis is the
most accurate part

of the skeleton for
sex determination.

And there are a number of
morphological differences

between males and females.

Here we have a male pelvis.

The difference is between
male and female pelvis,

are the most accurate way of
determining sex in individuals.

You will see that the
male pelvis overall

is much narrower and steeper,
whereas the female pelvis is

much shallower and broader.

If we look at this angle
here beneath the pubic bone,

you'll see it's much narrower
in males than it is in females.

There are a number of
other individual features,

and I'll go through each
of these in turn with you.

For comparison, here
we have a female pelvis

and as you can see, it's
much shallower and broader.

The subpubic angle is much wider
and the length of the pubis

is much longer.

And this is to increase the
size of the pelvic inlet

and pelvic outlet to
facilitate childbirth.

The first feature that I want to
show you, is the sciatic notch.

And you'll see here
on this female pelvis

that it's very
wide and V-shaped.

If we take a look
at the male pelvis,

you'll see that it's deeper,
narrower and more U-shaped.

I've included here an
intermediate example.

This one I've
included because it's

important to remember
that these features exist

on a sliding scale, from
very feminine to intermediate

to very masculine.

If you do have an
intermediate sciatic notch

and you're not sure whether
it's male or female,

it's useful to use
the composite arch.

Here, you follow the
edge of the sciatic notch

around the superior surface
of the auricular surface.

In males, you'll see that
it forms a continuous arch.

When you try to do
this in females,

you'll see that it misses
the superior surface

of the auricular
surface, and it forms

almost two separate arches.

This is another female pelvis.

And the feature that
I want to show you

is called the
pre-auricular sulcus.

That's this concavity underneath
the auricular surface.

This feature is not present in
all females, but when it is,

it tends to be quite
sharp and quite deep.

On males you'll rarely see
it, but if you do see it,

it tends only to be a
very shallow concavity.

Here are fragments of a
female pubis and a male pubis.

On the female, you can see
that the subpubic angle

is quite wide and U-shaped.

On the male, you can see that
it's quite narrow and V-shaped.

On the female, you can see that
the angle extends backwards

from the pubic symphysis,
whereas on the male

it just extends downwards.

Another feature to look at,
is called the ventral arc.

On females, this flattened
triangular area here

on the anterior
or front surface.

On males this is not present.

So overall the female
pelvis is much more gracile

than the male in terms of
the individual features,

they tend to be much sharper.

Another feature to
look at, is the length

of what's called
the iliopubic ramus.

You'll see that
it's much longer.

If we were comparing
it to the diameter

of the acetabulum,
the hip socket here,

this is much longer.

If we look at the male
pelvis, it's much shorter

and is approximately equal to
the diameter of the hip socket.

Overall, these elongated
features of the female

are about creating a larger
space to help with childbirth.

The skull is also very
useful for determining sex

in skeletal remains.

Overall, the male skull tends
to be more robust and larger

than the female skull,
whose features tend

to be a bit more gracile.

I'll go through a number
of the individual features

of the skull with you
that are useful in terms

of determining sex.

So here, we have a
male skull, and you'll

notice that the eye sockets are
much squarer than the female.

And the female they tend to
be more rounded and irregular.

The rims of the orbit
as well on the males

tends to be thicker and
blunter, whereas on the females

you can see that they're
actually quite sharp.

Another key feature is known
as the supraorbital ridge

or the brow ridge.

As you can see, it's much
more defined on the male,

and here on the female
it's quite smooth.

The center of this ridge is
referred to as the glabella.

And you can see that this
is quite pronounced here,

whereas on the female it tends
to be much less pronounced.

And as you can see on this
female it's completely absent.

Here we have a male and a female
skull viewed from the side.

Now, you can see
that the female skull

is much smaller than the male.

One feature you can also
see is that the fore head

of this female tends to be
a little bit more upright,

whereas the forehead of the male
tends to slope slightly further

backwards.

When we look at the
mastoid process which

is this feature
here, you can see

that the female mastoid process
is much smaller than the male.

The other feature
that you can see

is this ridge here above the
mastoid process in the male,

which is quite pronounced.

This is the posterior
zygomatic arch.

If we look at the
female, you can

see that it's smooth
above the mastoid process

and there's no pronounced ridge.

These are the same skulls
viewed from behind.

As you can see on
this male skull,

we've got a very
pronounced region here.

This is called the nuchal crest.

When we look at
the female you can

see that it's very smooth here.

These features are
related to musculature.

So they're essentially
muscle attachment points.

As a result of this, you do
get a great deal of variety

within and between
different populations.

So much like the
pelvis, the features

that we're looking at
form on a sliding scale

from very masculine
to very feminine.

And these differences will vary
between different populations

as well.

As a consequence, sex
determination in the skull

tends to be less accurate
than it is for the pelvis

because it is influenced by
factors such as lifestyle,

so diet activities and that
interaction with genetics.

Whereas sexual
dimorphism in the pelvis

relates to functional
morphology linked to childbirth.

Here we have two
femora, and it's

tempting to think that the
larger one is going to be male

and the smaller one
is going to be female.

In this instance, that is the
case, but it's not always.

We do have large
females and small males,

and there is a lot of overlap
between males and females

within a population.

When we're measuring the femora,
we can look at the length

and we can look at the
diameter of the femoral head,

and we can look at the
width of the condyles.

And we can look to
see whether these

fall into a female
or a male category.

But again, you must be
conscious of the fact

that there is a lot of overlap
between males and females,

and I would be very
cautious about assigning sex

on the basis of size alone.

So we've gone through
the different features

for establishing sex
from the skeleton.

One of the things
that I think it's

really important to remember,
is that sexual dimorphism

does vary slightly between
different populations.

So you will have to
accommodate this difference

when you're looking at your
own skeletal assemblage.

The other thing to remember
is that sexual dimorphism

is on a sliding scale from
very feminine, feminine,

intermediate,
probable male, male.

Skeletons don't just fall neatly
into two discrete categories.

So again, if you remember this
when you're establishing sex

in your skeletal assemblage.

In the next section,
we're going to focus

on estimating the age at death
of infant and juvenile skeletal

remains and the
variety of techniques

that we can use for
estimating age at death.

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