By Adam L. Brandt and Alfred L. Roca
Do conservation genetics and ancient Greek history ever cross paths? Recently, a genetic study of a remnant population of elephants in Eritrea has also addressed an ancient mystery surrounding a battle in the Hellenistic world. After Alexander the Great died unexpectedly in 323 BC, his generals divided his territory, founding several empires. Their successors ended up fighting each other during the next few centuries, often using elephants to intimidate the enemy and disrupt military formations. The Seleucids, heirs to the lands neighboring India, traded treasure and territory for access to Indian war elephants. They fought the Ptolemaic dynasty of Egypt, seeking control of the lands between the two empires during the Syrian Wars. The Ptolemaic pharaohs, desperate for their own pachydermal tanks, established outposts in what is today the country of Eritrea, to capture African elephants for warfare.
Elephants from the two continents were put to the test at the Battle of Raphia in 217 BC, between Antiochus III and Ptolemy IV Philopater. In The Histories, which includes the only known account of African and Asian elephants meeting in warfare, the Greek historian Polybius described the resulting fiasco:
“Most of Ptolemy’s elephants, however, declined the combat, as is the habit of African elephants; for unable to stand the smell and the trumpeting of the Indian elephants, and terrified, I suppose, also by their great size and strength, they at once turn tail and take to flight before they get near them. This is what happened on the present occasion; when Ptolemy’s elephants were thus thrown into confusion and driven back on their own lines.”
As every school child knows, Asian elephants are smaller than African elephants. So why did Polybius get this wrong? One British writer, perhaps unconsciously affected by the corporal punishments meted out by Classics teachers to disruptive students at English schools, decided that Polybius must after all be correct. He pointed out that, although African savanna elephants are larger than Asian elephants, there is a different species of elephant that lives in the tropical forests of Africa, and which is smaller in size than the Asian elephant. Thus began the tale that the war elephants of the pharaohs were actually African forest elephants, ignoring the thousands of kilometers that separate the range of forest elephants from places where the Egyptians captured their war elephants. This tale was then perpetuated by subsequent authors, each citing authors before as definitive sources.
A savanna elephant in Kruger National Park, South Africa
In a recent conservation genetics study, we examined the elephants of Eritrea, the descendants of the population that was the source of Egyptian war elephants. Eritrea currently has the northernmost population of elephants in eastern Africa. Perhaps one or two hundred elephants persist there, in isolated and fragmented habitat. Using DNA isolated from non-invasively collected dung samples we examined three different genetic markers. First we looked at slow-evolving nuclear gene sequences in the Eritrean elephants. In every case the sites always had the same sequence found in hundreds of savanna elephants, and in no case did we ever get a match to sequences found across all forest elephants. This established that Eritrean elephants were savanna elephants.
When we then looked at very fast evolving regions of the nuclear genome, the Eritrean elephants proved to be a close match to savanna elephants in East Africa, and again were genetically unlike forest elephants. Finally, we looked at mitochondrial DNA, which often has a different pattern than other genetic markers in elephants. Mitochondrial DNA is transmitted only by females, and these females do not geographically disperse away from the natal heard. Very often, one can infer a signal of ancient genetic events that persist only in the pattern of the mitochondrial DNA. Yet in this case, the mitochondrial DNA agreed with the nuclear results: these were savanna elephants, and there was not the slightest trace of any ancient forest elephant presence in Eritrea.
Given this result, why did Polybius claim that the Asian elephants were larger than African elephants? It turns out that in the ancient world there was a legend that, due to the wet climate, animals were always larger in India than they were elsewhere. This legend was widespread among authors before and after Polybius. Go back and look at the way the translation of the Polybius text is worded. Even in translation, it is evident that Polybius has interjecting his own beliefs onto the account, and not recounting an actual observation.
Our genetic study indicated that the isolated population of elephants in Eritrea has low genetic diversity. Habitat loss and human-wildlife conflict are major concerns for conservation of this population, which luckily has not yet been impacted by China’s lust for illegal ivory. Increasing and protecting suitable habitat for their long-term survival is critical, and in the very long run it may become possible to create habitat corridors to other surviving but distant populations. Luckily, the government of Eritrea is committed to protecting the country’s natural environment, and has recently reported an increase in the range and number of elephants.
Adam L. Brandt is a PhD candidate, and Alfred L. Roca is an Assistant Professor, in the Department of Animal Sciences of the University of Illinois at Urbana-Champaign. They are the authors of the paper ‘The elephants of Gash-Barka, Eritrea: Nuclear and mitochondrial genetic patterns‘ published in Journal of Heredity.
The Journal of Heredity covers organismal genetics: conservation genetics of endangered species, population structure and phylogeography, molecular evolution and speciation, molecular genetics of disease resistance in plants and animals, genetic biodiversity and relevant computer programs.
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Image credit: Savanna elephant in Kruger National Park, South Africa. By Felix Andrews (CC-BY-SA-3.0) via Wikimedia Commons.
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