Heterochrony and the paleoanthropological recordthe origins o the genus homo reconsidered

Résumé

In this paper a critical review is made of the main theories concerning the process of appearance and subsequent evolutionary success of the genus “Homo”. Furthennore, the current evidence coming from the paleoanthropological record is analyzed in arder to establish the interrelation between the biological and cultural factors impliccated in that process. It is suggested that the evidence of the paleoanthropological record presumably related to early “Homo” is basically explicable from the consideration of the strengthening of the social links in the bosom of the group, likely due to the abandonment of an hierarchyzed society in favour of a more cooperative one. This change does not necessarily imply, nor does it exclude the possibility of the formation of stable nuclear families, and probably appeared as a result of a biological change consisting of a decrease of the rate of development, that produced certain prolongation of all life history periods, and sorne delay in the offset signal for growth (but resulting in paedomorphic adults). As a consequence, there was an increase of the interactive and operative capacities that permitted the emergence of a novel and successful ecological niche under the new environmental conditions arised in the late Pliocene. Other additional heterochrony processes are suggested to explain the subsequent morphological evolution of the genus “Homo”.