This is a question that emerges frequently in seminars around ape and early hominin evolution. Why don't we have (non-human) apes at early hominin fossil sites and why don't we have earlier fossil records in the tropical forests of Africa, the main habitat for extant African apes? I am very interested in the question - and I am trying to understand what other researchers think about this. Any comments will be welcome, thanks!
The increasing of aridification since the Late Eocene caused many important extinction events. I recommended reading the following online version of:
Thomas L.P. Couvreur, et al., 2020, Tectonics, climate, and the diversification of the tropical African terrestrial flora and fauna.
Article Tectonics, climate and the diversification of the tropical A...
A fossil is always an exceptional conservation of a living being in terms of statistics, and if in addition a group of animals such as arboreal apes were quantitatively scarce and lived far from sedimentary environments such as fluvial, all this would explain their scarce presence in the fossil record.
Would love to obtain more (serious) opinions and foster discussion around this question! Thanks
Following what I heard from my colleague paleoanthropologists, four main reasons are commonly raised:
- Sedimentological context: bones do not conserve well in dense tropical sediments, due to the high pH coming from tree roots.
- Epistemological context: research attention was much more focus on East and South Africa since the discovery of the first fossils.
- Geographical context: it is always more difficult to organized expedition, especially archaeological investigations, in tropical forest.
- Geopolitical context: areas of geopolitical tension often discourage scientific projects and decreased the chance to obtain financial support.
I hope the answer will help.
René Bobe maybe you can help by offering your opinion here and see if that brings other opinions from fellow palaeoanthropologists to this discussion?
I personally find it very unlikely that early humans did not use tropical forest habitats at all. I think it is a question related to what gets fossilized in tropical forests habitats or nobody has searched enough. West and Central Africa have been quite politically unstable, particularly in forested areas, where armed forces hide, where progression is difficult, where fossil sites are hidden by vegetation and prospection is very difficult. Just a "bitaite".
There is a large bias in the sampling of the fossil record. Most localities come from temperate latitudes, and less research has been made in the tropical regions of the world.
This is partially related to the distribution of dry zones in middle latitudes, that provide zones with large extents of rock outcrops. This contrats with the extensive vegetation cover common in some tropical regions.
Another factor is the difference in infrastructure and academic personnel native to tropical countries, and devoted to searching and studing fossils in their own countries.
In geology when we do not find a fossil deposit, whatever they are, it is, either because we have not looked in the right place or because such a deposit does not exist. When a species begins to expand there are fewer specimens, then, if it is successful, the number of individuals begins to increase. And therefore, when he dies, his remains are more frequent. The answer to your question is any of these. This is, at least, my way of seeing things as a geologist that I am.
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