# The School of Biosciences

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## Put the fossils in the following order2: (This sequence represents the proposed sequence of evolution of these hominids)

1. Ramapithecus

2. Australopithecus africanus

3. Homo habilis

4. Homo erectus

5. Homo ergaster

6. Homo sapiens (cro magnon)

7. Homo sapiens (modern)

• ## You have not used all the replicas – where do you think the others fit in the sequence?

• How might material from juveniles and different sexes affect the analysis?3

## Exercise 2, Evolution of brain size: Variation

If you only have a small number of fossils you will need to have some idea of the variation in the character you are measuring in order to decide if you have two members of the same species or two members of different species4.

In this exercise we will get an estimate of the brain size of the people in this room to get a feel for the amount of variation in a population.
For the human skull(s) look at how the brain fills the cranium. The space it is in can be defined by the brow ridges and the hole behind your ear (the mastoid process)5. Obviously your neck prevents you following your brain case right round as you can for the skull, so you will have to guess this bit. Estimate your own brain size use the following procedure:

 Lay your head (ear down) on a piece of A3 paper. Get a friend to draw round your head. Draw a line between the ends of your trace to complete the shape

 Draw a straight line from the brow ridge where you started drawing to the back of the skull. Measure the length of this line to the nearest half cm: this is the skull width. Draw a second line from the mastoid process where you stopped drawing to the top of the skull. This line should be at approximately 90o to the width line. Measure the length of this line to the nearest half cm: this is the skull height.

Calculate the average skull diameter by taking the average of the height and width. Read your brain volume from the table on the next page6. Record this value here:

My brain is cm3
Enter your brain size in the male or female column on the laptop. Also, weigh yourself and put your weight next to your brain size7 – this information will be important in interpreting the data. You will see a graph of males and female cranial sizes appear as you put in your data8.

• Is there a difference between male and female brain size?

• If there is difference between male and females, can you think of a reason for this? (it might help to look at a plot of weight vs. brain capacity)

 Skull average diameter Brain capacity 8 148 8.5 183 9 223 9.5 270 10 323 10.5 383 11 450 11.5 526 12 611 12.5 704 13 808 13.5 922 14 1047 14.5 1184 15 1333 15.5 1495 16 1671 16.5 1861 17 2066 17.5 2287 18 2524 18.5 2778 19 3050 19.5 3340 20 3649 20.5 3979 21 4329 22 5094 23 5952 24 6908 25 7969 26 9141 27 10432 28 11848 29 13397

Exercise 3: Clever than an ape9? How has brain size changed during evolutionary time?

Brain size is one character used in classifying hominoid fossils. Estimate the cranial volume of the skulls using the same procedure you used for yourselves. Put the data in the table below.

 Age (Million Years ago (MYA) Brain size (cm3) Paranthropus boisei 2 Homo habilis 2.5 Australopithecus africanus 3 Homo erectus 1 Homo sapiens (modern) 0 Homo neanderthalensis 0.1 Pan troglodytes 0 Ramapithecus 7.5 Homo ergaster 2.0 Homo sapiens (cro magnon) 0.04 Gorilla gorilla 0 Me 0

Plot a graph of age vs. brain size (put yourself on if you dare!!10).

 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5

Age (MYA)

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