Simply over 20 years in the past, as the brand new millennium started, it appeared that tracks left by our historic human ancestors courting again greater than about 50,000 years have been excessively uncommon.
Solely 4 websites had been reported in the entire of Africa at the moment. Two have been from East Africa: Laetoli in Tanzania and Koobi Fora in Kenya; two have been from South Africa (Nahoon and Langebaan). The truth is the Nahoon website, reported in 1966, was the primary hominin tracksite ever to be described.
In 2023 the scenario could be very completely different. It seems that folks weren’t wanting onerous sufficient or weren’t wanting in the best locations. Immediately the African tally for dated hominin ichnosites (a time period that features each tracks and different traces) older than 50,000 years stands at 14. These can conveniently be divided into an East African cluster (5 websites) and a South African cluster from the Cape coast (9 websites). There are an additional ten websites elsewhere on this planet together with the UK and the Arabian Peninsula.
Provided that comparatively few skeletal hominin stays have been discovered on the Cape coast, the traces left by our human ancestors as they moved about historic landscapes are a helpful solution to complement and improve our understanding of historic hominins in Africa.
In a not too long ago printed article in Ichnos, the worldwide journal of hint fossils, we supplied the ages of seven newly dated hominin ichnosites that we have now recognized prior to now 5 years on South Africa’s Cape south coast. These websites now kind a part of the “South African cluster” of 9 websites.
We discovered that the websites ranged in age; the newest dates again about 71,000 years. The oldest, which dates again 153,000 years, is likely one of the extra outstanding finds recorded on this research: it’s the oldest footprint so far attributed to our species, Homo sapiens.
The brand new dates corroborate the archaeological file. Together with different proof from the world and time interval, together with the event of refined stone instruments, artwork, jewelry and harvesting of shellfish, it confirms that the Cape south coast was an space through which early anatomically trendy people survived, developed and thrived, earlier than spreading out of Africa to different continents.
Very completely different websites
There are vital variations between the East African and South African tracksite clusters. The East African websites are a lot older: Laetoli, the oldest, is 3.66 million years previous and the youngest is 0.7 million years previous. The tracks weren’t made by Homo sapiens, however by earlier species corresponding to australopithecines, Homo heidelbergensis and Homo erectus. For essentially the most half, the surfaces on which the East African tracks happen have needed to be laboriously and meticulously excavated and uncovered.
The South African websites on the Cape coast, against this, are considerably youthful. All have been attributed to Homo sapiens. And the tracks are usually totally uncovered after they’re found, in rocks often called aeolianites, that are the cemented variations of historic dunes.
Excavation is subsequently not normally thought-about – and due to the websites’ publicity to the weather and the comparatively coarse nature of dune sand, they aren’t normally as nicely preserved because the East African websites. They’re additionally weak to erosion, so we regularly must work quick to file and analyse them earlier than they’re destroyed by the ocean and the wind.
Whereas this limits the potential for detailed interpretation, we are able to have the deposits dated. That’s the place optically stimulated luminescence is available in.
An illuminating technique
A key problem when finding out the palaeo-record – trackways, fossils, or some other type of historic sediment – is figuring out how previous the supplies are.
With out this it’s troublesome to guage the broader significance of a discover, or to interpret the climatic modifications that create the geological file. Within the case of the Cape south coast aeolianites, the courting technique of selection is commonly optically stimulated luminescence.
This technique of courting reveals how way back a grain of sand was uncovered to daylight; in different phrases, how lengthy that part of sediment has been buried. Given how the tracks on this research have been shaped – impressions made on moist sand, adopted by burial with new blowing sand – it’s a good technique as we could be fairly assured that the courting “clock” began at about the identical time the trackway was created.
The Cape south coast is a good place to use optically stimulated luminescence. Firstly, the sediments are wealthy in quartz grains, which produce numerous luminescence. Secondly, the ample sunshine, large seashores and prepared wind transport of sand to kind coastal dunes imply any pre-existing luminescence indicators are totally eliminated previous to the burial occasion of curiosity, making for dependable age estimates. This technique has underpinned a lot of the courting of earlier finds within the space.
The general date vary of our findings for the hominin ichnosites – about 153,000 to 71,000 years in age – is in keeping with ages in beforehand reported research from comparable geological deposits within the area.
The 153,000 12 months previous monitor was discovered within the Backyard Route Nationwide Park, west of the coastal city of Knysna on the Cape south coast. The 2 beforehand dated South African websites, Nahoon and Langebaan, have yielded ages of about 124,000 years and 117,000 years respectively.
The work of our analysis group, based mostly within the African Centre for Coastal Palaeoscience at Nelson Mandela College in South Africa, shouldn’t be performed.
We suspect that additional hominin ichnosites are ready to be found on the Cape south coast and elsewhere on the coast. The search additionally must be prolonged to older deposits within the area, ranging in age from 400,000 years to greater than 2 million years.
A decade from now, we anticipate the record of historic hominin ichnosites to be lots longer than it’s at current – and that scientists will be capable of be taught a fantastic deal extra about our historic ancestors and the landscapes they occupied.