11.   We can not, of course, replay a piece of history and we do not have a fossil record of behaviour.

12.   We know about them from fossil records.

13.   We shall concentrate on the arthropods with the best fossil record.

14.   We now know that this hominid, with the tongue-twisting name of Australopithecus, disappeared from the fossil record approximately one million years ago.

15.   An advantage is that it relies on a single thumb bone, not a complete hand, and one that is well represented in the fossil record.

16.   And finally, the fossil record reveals, the Asian members of the Homo erectus species ultimately became extinct too.

17.   At the time, there was no fossil record of Precambrian life of any kind, not even single-cell bacteria or algae.

18.   But the problem with that theory is that the massacre depicted in the global fossil record is turning out to be far from uniform.

19.   But when the two lines of primates diverged had seemed to be lost in the wide gaps in the fossil record.

20.   Consequently, until more information is available, Haile-Selassie said that Orrorin could fill any one of several places in the fossil record.