Before the Sahara Desert ended up as a desert region, 12,000 years ago, the atmosphere in southwestern Libya was a landscape in which water and life flowed. This is the conclusion of a team of palaeontologists who have discovered 17,551 identifiable remains in the Tadrart Acacus mountains. Of all these animals, 80% were fish remains - like tilapias and catfish - that fed the first humans during the Holocene period.
The remains, which experts claim cut-off signs and burn marks on the bones reveal that the fish were eaten by the humans who used that shelter, date from 10,200 to 4,650 years ago, and span much of the early Holocene period, the present geological epoch. The rest of the remains consisted of mammals (about 19 percent) and a small number of bird, reptile, mollusc and amphibian remains.
It is not the first time that fish remains have been found in what are now dry and arid desert regions, but the team says it is the first time that ancient climate has been traced through animal remains.
“The other discoveries are surface finds, of only one layer, one period, one event. Whilst what we have here is a sequence of 5,000 years with many bones, that makes it special," explained Wim van Neer of the Royal Belgian Institute of Natural Sciences, co-author of the study, which has been published in the open access magazine PLOS ONE.
Multiple human settlements and diverse wildlife
The rocky shelters within the Tadrart Acacus preserve not only important flora and fauna remains, but also important cultural artefacts and rock art due to the early occupation of these shelters during the Holocene. Experts identified and dated the animal remains found at this site and investigated changes in the abundance and type of these animal remains over time.
They also found that tilapia decreased significantly over time, which may be because catfish have the ability to breathe air out of the water and survive longer in warm, shallow waters.
Researchers believe that this disappearance of the fish occurred as the number of mammals increased, suggesting that humans living in the mountains relied on hunting to survive.
"This study reveals the ancient hydrographic network of the Sahara and its interconnection with the Nile, providing crucial information on the dramatic climate changes that led to the formation of the world’s largest desert," the authors clarify.
"Takarkori’s rocky retreat has once again proved to be a real treasure for African archaeology and beyond: a fundamental place to rebuild the complex dynamics between ancient human groups and their environment in a changing climate," they conclude.
The findings coincide with previous evidence from the Sahara, including sediments and geological characteristics, which led to a change in climate from a wetter environment with vegetation and abundant lakes more than 10,000 years ago, a period of fluctuating dry and wet conditions, until about 5,500 years ago. The region became increasingly arid, resulting in the landscape we can see today.
Reference: Van Neer W, Alhaique F, Wouters W, Dierickx K, Gala M, Goffette Q, et al. (2020) Aquatic fauna from the Takarkori rock shelter reveals the Holocene central Saharan climate and palaeohydrography. PLoS ONE 15(2): e0228588. doi.org/10.1371/journal.pone.0228588