A new study from the Indian Institute of Science Education and Research (IISER), Mohali, reports the discovery of Pleistocene (2.58 – 0.63 mya) fossils from hitherto unexplored fossil rich areas in the Upper Siwalik group of the Himalayan Mountain Ranges. The explorations, spanning over the last two years, have yielded teeth and bones of ancestral species of modern-day buffaloes, nilgais, wildebeests, horses, elephants and even porcupines – some of them now locally extinct. But a rather unexpected and striking find has been that of an ostrich eggshells in the Upper Siwaliks.
That the ostrich once lived in this region has significant implications with respect to our understanding of the past climate in the northern part of the Indian subcontinent. The ostrich prefers an open, cooler and dry climate; and its presence in what are now the foothills of the Sivaliks indicates time periods when the ‘Indian summer monsoon was weakened,’ allowing ostrich populations to exist in the area. This conclusion fits in fairly well with previous climate research in the area over the last three decades, which have attested to a breaking up of dense forests and giving way to more open grasslands due to weakening in the Indian monsoon, a transition that only became more pronounced during Late Pleistocene (~0.12 – 0.01 mya).
“However, since no ostrich remains to date have been recovered in peninsular India from this time frame (ie the Pleistocene), it could very much mean that suitable dry habitats for the ostrich had not yet developed in peninsular regions,” Anubhav Preet Kaur, the author of the study, said in a communication with indianexpress.com.
This is hardly the first time an exploration for fossils has taken place in the Himalayas, and these mountains have been subject to such palaeontological investigations for over two centuries. As previous palaeontological records show – it is not unusual to find remains of birds and animals whose habitat requirements were remarkably different from conditions that exist in the region today. Interestingly, specialist palaeontologists – people who study fossils – joined the action quite late.
The first fossil hunters
One of the first systematic observations on Himalayan palaeontology were, interestingly, made by Hugh Falconer, a British surgeon posted in Calcutta who initially was a believer in Creationism! While working at the botanical gardens in Saharanpur, Falconer had identified fossil bones of crocodiles and tortoises during surveys in the Siwaliks, which were then reported in an 1832 paper in the Journal of the Asiatic Society. Most of these early surveys and discoveries in the Siwaliks were assisted – in no small measure – by Falconer’s friends in the British Army and the local Raja of Nahun.
Around the late 1840s, working with Proby Cautley, a civil engineer deployed in the area to construct canals, Falconer would find remains of the hippopotamus, elephant and cranes and cranes as well. These findings showed that the area had once been a swamp and marsh – relatively humid conditions existed than they do today.
But it was not until 1913 when Guy Pilgrim, a geologist from the Royal Society who was appointed with the Geological Survey of India (GSI), would chalk out different formations in these mountain ranges based on the characteristic animals whose fossils he found.
Ostrich eggshells through space and time
Despite being rich in fossils, the Siwaliks pose their own challenges. ‘Unlike the Siwaliks exposed in Pakistan, that are largely barren, the Siwaliks in India are covered with a significant amount of vegetation, making exploration a challenge,’ explained Kaur. Further, ‘the Indian Siwaliks are quite steep, and the deposition of fossil-containing-sediment on the foothills is a result of extensive transportation and churning, destroying many fossils in the process,’ she added. The process is fairly unpredictable and takes thousands of years, the geologist having absolutely no control over it. In order to make the most of her fieldwork, she gave a computer modelling software an input of previously known fossil locations, in order to narrow down to locations with a higher probability of yielding fossils. Of the ten localities in the Siwaliks she explored, only six of them yielded fossil assemblages.
Biological remains buried and churned for millions of years are often broken in nature, making it incredibly difficult for scientists to correctly diagnose which species is belongs to. Eggshells are no exceptions. ‘However, these ostrich eggshell fragments luckily survived multiple erosive and destructive processes by virtue of being thick (~2.2 mm). Moreover, eggshells of every species that reproduces by eggs has characteristic pore patterns. I, therefore, passed recovered eggshell remains through a stereomicroscope to identify pore morphology,’ Kaur elucidates. The blue-necked ostrich species (molybdophanes), to which the eggshells belonged, is now restricted to portions of north-east Africa (largely around Ethiopia, Somalia and Kenya).
An earlier, 2008, study in Morocco had also reported on ostrich bones and eggshells of the now-extinct Asian ostrich, which had dominated the landscapes of South/Central Asia and the Middle East during the Pliocene (3.6 mya) – Holocene (11.7 kya) periods. While ostrich bones have been reported from the Siwaliks in 1884 by the Geological Survey of India, this is the first time eggshells have been recovered from this particular geographical and geologic context.
Being a species that lives in a grassy, environment, ostrich remains – albeit few and far between – have been considered to be reliable proxies of what rainfall and temperature conditions in those regions were like. Although no continuous fossil record of ostriches exists in geologic contexts, carbon isotope signatures of whatever eggshells have been recovered show a clear transition from wetter to somewhat-drier conditions (and, therefore, woody to grassland type communities) through the Pleistocene. These assessments dovetail quite well with isotope studies conducted on other biological archives from these time periods. It seems plausible, therefore, that populations of ostriches, or related species, that ostrich populations expanded into North/North-Western India where the environment was just right for them – not too arid and not too wet either.
Previously, a 2015 study had reported ~60000 year old ostrich egg-shell remains in Rajasthan, and examining ancient DNA in eggshells confirmed the presence of the ostrich in North West India at least until ~24000 years back. However, with the lack of a continuum in the fossil record, it is difficult to establish an evolutionary relatedness between the Early/Middle Pleistocene populations that Kaur (2022) examined, and the ones in Late Pleistocene. What led to the ultimate extirpation of the ostrich from these areas during the Late Pleistocene-Early Holocene is not entirely clear. For the time being, a further transition to an even drier climate, leading to desert-like arid conditions in North West India, remains one of the few possible explanations.
The author is a research fellow at the Indian Institute of Science (IISc), Bengaluru, and a freelance science communicator. He tweets at @critvik
The ostrich prefers an open, cooler and dry climate; and its presence in what are now the foothills of the Sivaliks indicates time periods. (Representative Image) 
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