The School of Biosciences



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What does the H/F index tell you about how an animal moved around?


Calculate the index for the modern and fossil hominids.







Humerus length

Femur length

Humero-femoral index

Modern human

HS_modern_HF.jpg












Gorilla

Gorrilla_HF.jpg












Chimp

Chimp_HF.jpg












Me (i.e. you)









Homo ergaster


(Ergaster_HF.jpg










Australopithecus afarensis

Picture










Homo Neanderthalensis

picture












Appendix


Human Skeletal Characteristics guide
SEX

The pelvis
In general the female pelvis is broader than the male due to it forming the birth canal. The greater width of the female bony pelvis manifests itself in a number of ways. An important area is the sub-pubic angle of the pubic bone, part of the front of the pelvis shown with arrows in Figure 1. In females it tends to be wider and more U-shaped whereas in the male it tends to be narrower (generally less than 90º) and more V shaped.


One of the clearest distinctions between the male and female pelvis is the Sciatic Notch (indicated by the arrows in Figure 2).This is situiated on the posterior part of the pelvis. It is wider and shallower in females than in males, which is another manifestation of the broader female pelvis.


Figure 2

The sacrum (your tail bone!) at the back of the pelvis also gives an indication of sex. In the female the coccyx (the very tip of the sacrum) is relatively and absolutely smaller in comparison to the rest of the sacrum than in the male.



The Skull





Figure 4

Key areas of the skull for determining the sex of skeletons are shown in Figure 4. The Brow Ridge (1) is more developed in the male and the forehead is more sloping. In the female the brow ridge is smaller and the forehead more vertical. The Mastoid Processes (2) and the Nuchal Crest (3) are more developed in the male.
The Mandible

Figure 5

The mandible (jaw bone) is comparatively shorter, narrower, more gracile and lightweight in females than in males (Figure 5). Males also have a squarer chin than females, often with a slight dimple.

The Goneal angle (Figure 6) is another indicator of sex in the mandible. In females it is generally obtuse (>125°) and rounded, whereas in males it is acute (<125°) and more rectangular.



1 Note for teachers: see the Introductory lecture on Human evolution on the web site which may provide useful background material.

2 This is asking about the morpho species concept but takes no account of variation within a species. It helps to focus on qualitative differences rather than quantitative ones

3 There are pictures of juvenile skull material on the web site

4 The students will need to be familiar with the biological and the morpho (or phenetic) species concepts to fully grasp this.

5 Students nearly always fail to get to the mastoid process and therefore underestimate their brain size.

6 Note for teachers: this is based on an empirical relationship – it tends to overestimate when used by enthusiastic students. You can tweak the number down if needed. You may need to reassure small brained pupils that this is not a real measure of brain size! I usually discuss the various sources of error at this point.

7 You may get some problems with measuring weight – stress that this is anonymous, the computer and the scales can be sympathetically placed

8 Plot males and females separately. Weight and brain size usually show sexual dimorphism but the ratio does not. This is useful in discussion of what a species is. For fossils you have to use the morpho-species concept (not the biological species concept). If there is significant sexual dimorphism then males and females would be classed as different species.


9 A leading question – this invariably stimulates debate about whether a large brain makes you more intelligent and indeed, the nature of intelligence.

10 Brain size should increase in our ancestors, but remains around 400 cm3 in chimps. Worth pointing out that both we and chimps are equally fit (i.e. we are here at present). A large brain is not necessary for evolutionary success. Indeed it is useful to consider both costs and benefits of a large brain.

11 Note for teachers – see the power point pictures of skeletons on the CD – these have been used with primary school kids to introduce the idea of the humero – femural index but are probably a good introduction to this practical.

12 You really need a full human skeleton for this

13 There are male and female skull pictures on the web site

14 If you can’t get a relationship use Height (cm) = 2.6 x Femur length (cm) + 65

15 Plot males and females separately. Femur length and height usually show sexual dimorphism but the ratio does not. This is useful in discussion of what a species is. For fossils you have to use the morpho-species concept (not the biological species concept). If there is significant sexual dimorphism then males and females would be classed as different species.

16 There is a simpler practical exercise that introduces the concept of the humero-femural index (skeleton femur humerus introduction.ppt)
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