Footprints Bring Fossil Elephants to Life
How similar were ancestral elephant species to our two remaining species?
That may be a question you don't ask very often. Dr Faysal Bibi and several co-authors in the Royal Society Journal Biology Letters have more or less answered it Social behaviour is one of the most enlightening and evocative interests of the human animal. We love to read about ourselves and how dogs, monkeys and even ants are our inferiors on the social scale. Could it be that elephants are our superiors in matrilocal (mother-based), hierarchical and complex social structures?
Mleisa lies in the UAE. And adds significantly to our rich record of our proboscid friends in the fossils. Mastodons and mammoths seem to have social structure in the Pleistocene (5-5 mya), but what about the evolution of these intensely sociable group of animals.
Elephant track-ways in North America and Europe are also known from the Miocene. Here, though at up to 8 mya (Late Miocene), we have a herd and an individual recording their complexity of movement in the earth on 14 track-ways.
Drs. Bibi and Kraatz discussing preliminary mapping at the Mleisa 1 site (14 Jan 2011.) - Credit: © Mathieu Schuster
All tracks are more or less contemporary. The 260m track-way is one of the world's longest while many others are parallel, giving indications of a simultaneous herd movement. Regular trails could cause this effect, but you would expect some overlap/intersection and there is none.
Without over-emphasising the logic, one large individual seems to be keeping (himself) a small distance from the herd nearby. One herd individual, among 13 possible individuals, matches the mean stride length of the "loner." These two individuals have a mean stride length of >3m, while a miniature example with faint (perhaps light) footprints has a small stride.
Unlike the Loxodonta (African) and Elephas (Asian) elephants, the body masses in the UAE are estimated higher than the adult females of these two species. The joint authors draw several ideas from this data. With males assumed the larger sex, the "loner" would have been at least mature in age. It could be that the females presumed to constitute the herd were normally around the male size, with little sexual size difference.
Other fossil evidence needs to be investigated to decide this is possible. In fact the size and number equation pretty much approaches the two modern species. The late Miocene and early Pliocene does have fossil Loxodonta and Elephas spp., but this area has many Stegotetrabelodon syrticus and a few Deinotherium and Mastodon specimens . So far there is no method to determine which species made these precious prints, or even if the solitary track is of the same species as the herd.
The extinct Stegotetrabelodon herd reconstructed from fossil evidence! - Credit: © Mauricio Anton
The best estimate would be the common Stegotetrabelodon because it used open habitats, with evidence of the customary male-based natal dispersal system, with matriarchs in charge of the herds. At least, we now have direct evidence for the first time that the first modern elephants seemed to have a social system we can recognise from extant herds in Africa and Asia.
Dr William J. Saunders of the University of Michigan assesses the authors success in: "Bibi et al.'s analysis of the trackways reveals evidence of the body size, stride length, pace, and social structure of their makers, and is important because it confirms that the complex social behavior of modern Asian and African elephants, in which herds are led by matriarchs and adult bull males live primarily solitary existences, extends back at least to the very origins of elephants."
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