Clarity and Confusion

Interesting things I am learning about in class, which are confusing me and making me think:

1) A fossil hominin is found and dated to, let say 3 million years old, then one is found and dated to 6 million. The date alone is only a very minor part of how its relationship to other extinct species is inferred. The 3 million year old specimen can have features that are more ancestral than the 6 million year old one. Morphological features do not change uniformly over time or through lineages, and human evolution is far from linear. Interesting and confounding.

2) A novel feature in a fossil may enable it to be grouped with other fossils that share the same new feature, and differentiate it from an older more ancestral group that does not show this structure. But then, that same new feature is ancestral relative to an even more contemporary form. There is much discussion in Paleoanthrology about shared novel, or as they say “derived” features, being the crux of inferring species relationships of extinct hominins. And I just wanted to put it in words that, like most things, it is all relative.

3) After reading the material it is clear that scientists are splitting hairs to determine the best species category for these extinct ancestors. But I was thinking the other day that grouping living organisms into species is possible and obviously practical, but what of these extinct species relationships? Time is a factor that throws some current species concepts on its head and might it suffice to say that these were all human ancestors, one way or another, and to form one species distiction for all extinct hominins, like “Homo extinctus” and end it there. But I suppose that would be maximally uninteresting and would put a lot of hard working people out of work.