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)



    • Think about the difference between individuals 2 and 3 – what characteristics mean that Australopithecus africanus is not in the genus Homo?

    • Compare 4 & 5 with 6 & 7; what features do you think justify the classification of 6 & 7 into sapiens?

    • 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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