TABLE 1 Species of Australopithecus, Homo, and modern African apes with geological ages, estimated body weights, brain volumes, relative brain sizes (EQ), cheek-tooth area, and relative cheek-tooth area (MQ)

 

 

Body weight, kga

Brain volume,b

Tooth area,

Species

Dates, (My)

Male

Female

(cc)

EQc

dmm2

MQe

A. afarensis

4–2.8

45

29

384

2.2

460

1.7

A. africanus

3–2.3

41

30

420

2.5

516

2.0

A. aethiopicus

2.7–2.3

 

 

399

 

688

 

A. boisei

2.1–1.3

49

34

488

2.6

756

2.5

A. robustus

1.8–1.0

40

32

502

2.9

588

2.2

H. habilisf

2.4–1.6

52

32

597

3.1

502

1.7

Early H. erectus

1.8–1.5

58

52

804

3.3

377

1.0

Late H. erectus

0.5–0.3

60

55

980

4.0

390

1.0

H. sapiens

0.4–0

58

49

1350

5.8

334

0.9

Pan paniscus

0

38

32

343

2.0

227

0.9

Pan troglodytes

0

49

41

395

2.0

294

0.9

Gorilla gorilla

0

140

70

505

1.7

654

1.0

a See refs. (McHenry, 1992 and 1994).

b Endocranial volume is transformed into brain volume by formula 4 in ref (Aiello and Dunbar, 1993).

c EQ is the ratio of brain volume and expected volume. Expected brain volume is 0.0589 (species body weight in g)0.76; see ref. (Martin, 1981).

d Tooth area is the sum of the md × bl diameters of P4, M1, and M2 ; see ref. (McHenry, 1984).

e MQ is the ratio of observed tooth area and expected area; expected area is 12.15 (species body weight in kg)0.86. See ref. (McHenry, 1988).

f Two species may be represented in this sample. Using Wood's 1988 classification, I calculate the values for H. habilis sensu stricto and Homo rudolfensis as follows: male body weight, 37 and 60 kg; female body weight, 32 and 51 kg; brain volume, 579 and 709 cm3; EQ, 3.5 and 3.0; tooth area, 478 and 570 mm2; MQ, 1.9 and 1.5 kg; see ref. (McHenry, 1994b).



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