Hominization, Issues in

One of the most important discoveries of recent times, related to our origins, is the verification of a close genetic affinity between human beings and chimpanzees. Such affinity is so significant (98.8%)that it is estimated that both phylogenetic lines that led to the two species had a common ancestor approximately 6 to 8 million years ago. Since that moment, and after the branching occurred, begins the most amazing and passionate history, that of our own family.

The “hominization process” refers to the origin and evolution of the hominid family (forms that comprise both our ancestors and ourselves). When trying to reconstruct this process, paleoanthropology acquires an especial relevance, because while giving us the historic evolutionary fundamentals of man, it shows us the same basics of anthropology as science. If the uniqueness of this is its approach to man as a bio–psycho–socio–cultural unity, that of paleoanthropology resides in its intent to answer the question of how this unity was developed.

Hominization was not only a process of biological transformation nor a simple adding of unidirectional causes and effects. On the contrary, we think that this process was a complex event, characterized by the succession of particularly significant synergic phenomena resulting from a dynamic interaction of biological, psychological, spiritual, social, and cultural variables.

Our knowledge about this process has undergone remarkable improvement during the last decades. Nevertheless, there are still some questions of complex solution. One of them derives from the fact that when we go back in time to track down our biological past in search of our own family first members, we face a great difficulty in identifying them in the fossil record. In our opinion, the main reasons for this difficulty are the following:

• 1.
  The material known until now, between 4 to 8million years ago, is barely representative due to its scarcity and to its being usually fragmented and deteriorated.
• 2.
  To define which are the physical features that show hominid nature in a fossil is an act always conditioned by each historical moment ideology.
• 3.
  Despite the current establishing of these features, the valuations of fossils' anatomic traits are so varied that they do not obtain consensus among scientists.

The first reason becomes obvious if we think about the amount and quality of available material to be studied and analyzed by specialists. As for the second, we discuss below two illustrating occurrences: the famous Piltdown “discoveries” and the one performed by the so-called ramapithecines. In both cases, we will see how they were highly valued in their moment, for they clearly fulfilled the expectations of the time. Finally, we will discuss the varied interpretations supported at present concerning the finds of likely hominids with over a 4-million-year dating.

In the first decades of the 20th century, scientists thought that the most significant hominization phenomenon was the development of the brain. In this way, the existence of a decisive step or “cerebral Rubicon” was supposed, between 700 to 800 cc, the so-called step to reflection. Therefore, a skull fossil with a cranial capacity below700 cc could not be regarded as human, while one over 800 cc could.

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