Are early hominds only found in Africa as a result of better preservation conditions?

Question

In Oz the acidic nature of he soils make finding old bones rare as they need to have died in situations that are rare to find in Oz.

Answer 1

I would say the answer is generally yes but I don't know what Oz is.  Africa has the Great Rift Valley.  This is a feature formed from the separating plates.  This rift has exposed fossils of relatively recent age (3 million years and less).  Generally any particular place is either in a basin where sediments continue to pile up  after many thousands of years and are eventually buried thousands of feet deep, or they are in area of erosion where their remains will be washed away within several thousands of years.  The Rift provides the conditions where fossils of suitable age are exposed.  This is relatively rare.  Since the subcontinent of India crashed into Asia, there really are not as many good places to look for fossils of suitable age.

Answer 2

Not the ONLY reason...

But since there were probably more hominins in Africa, and earlier there than anywhere else, that is also probably a contributing factor!