Question

Based on morphological evidence, do you think that the genera Homo and Australopithecus represent different grades? Explain your answer based on morphological differences observed between these two genera.

Answer 1

Austrolopithicus species, perhaps is the next stage in evolution after Apes  showed skeletal and other bones characters which are more comparable and extension of the characters of the present Apes. These skeletal features included small brain size, receding frontal skulls, large orbits, longer hand bones, suggesting that they are more arborial (spend time on trees) etc.

Homo  is the genus that emerged from Australopithecus indicates human like forms characterized by a relatively large cranial capacity, limb structure adapted to a habitual erect posture and a bipedal gait, well-developed and fully opposable thumbs, hands capable of power and precision grips, and the ability to make standardized precision tools.

The key adaptive characteristics of the hominids indicate that at least three grades have appeared in the course of human evolution. The first grade is characterised by body mass less than 50kg, stature of less than 130cm, facultative bipedalism, a large masticatory system, small brain, ape like developmental structure. The second grade is characterised by body mass more than 50kg, stature of more than 160 cm, a relatively small masticatory system an EQ of less than 4.5 a short ape like maturation period. The third grade is almost similar to second but exihibit high degree of encephalisation and delayed maturation. All Austrolopithicus sp comes under the first grade. Homo sp comes under second and third grade. the most advanced Homo sapiens comes under third grade.