Question

• What is the difference between Homo erectus / Homo ergaster and Homo heidelbergensis in terms of brain case (the part of the skull containing the brain)?
• Do you see any variations about the teeth between Homo erectus / Homo ergaster and Homo heidelbergensis?
• How does Homo erectus / Homo ergaster differ from Homo heidelbergensis in facial terms, including the jaws (and jaw projection)?
• Homo heidelbergensis is a species that is considered to be an evolutionary step closer to us (humans) than Homo erectus/Homo ergaster was. Why do you think this is so?

Answer 1

THE difference between Homo erectus and Homo heidelbergensis in case of skull are as follows :-

In Homo ergaster ---

Brain

• average brain size was approximately 860 cubic centimetres and made up about 1.6% of their body weight.

Skull

• had developed a more human-like shape including a higher, more domed cranium or braincase. Unlike modern humans, the cranium had a moderate post-orbital constriction (indents behind the eye sockets). This feature is linked to brain size. As our ancestors’ brains expanded, their skulls became fuller and more rounded with increasingly smaller post-orbital constrictions.face projected outward but to a smaller degree than in earlier ancestors.
• nose was human-like for the first time. It now projected outward whereas earlier species had flat noses.

In Homo heidelbergensis -----

Brain

• brain was large, averaging approximately 1250 cubic centimetres in size, representing 1.9% of their body weights.

Skull

• small post-orbital constriction behind the eye sockets.

IN variation of teeth - Homo heidelbergensis have

some members of this species possessed a gap, called the retromolar space, behind the third molars (or wisdom teeth) at the back of the jaw. Others had only a tiny gap or no gap.

In Homo ergaster have

• arrangement of the teeth within the jaws was intermediate between that of apes and modern humans in that the side rows of teeth were much further apart at the back of the jaw than at the front
• canine teeth were modern in form, being short and blunt like those of modern humans.

IN terms of facial - Homo heidelbergensis have -

Lower jaw was strongly built for the attachment of strong chewing muscles

As with earlier species, the lower jaw did not have a protruding  pointed chin.

IN Homo ergaster have-

• jaw was shorter and more lightly built than those of earlier species, resulting in a flatter, shorter face
• like earlier species, the front of the lower jaw sloped backward and did not form a pointed chin like that of modern humans.