Â鶹ÒùÔº

The thylacine, also known as the Tasmanian tiger or Tasmanian wolf, roamed the Australian mainland, Tasmania and New Guinea for millions of years, up until the last one died in Tasmania in 1936. Despite the names, the thylacine was neither a tiger nor a wolf, but actually a marsupial relative of the Tasmanian devil.

It was long thought that the extinction of the thylacine was mainly due to competition with newly introduced dingoes and extermination by humans, who tended to think of them as pests. However, a new study, in Proceedings of the Royal Society B: Biological Sciences, indicates that there was more to their decline than previously thought.

The study authors, Buddhabhushan Girish Salve and Nagarjun Vijay, believed that genetics may have played a role in the thylacine's eventual extinction, which was helped along by dingo competition and hunting practices. The researchers tested out their hypothesis by comparing the thylacine genome to those of the Tasmanian devil and other related marsupials, using machine learning-based comparative genomics tools to search for lost genes and estimate the timing of gene loss with molecular evolutionary methods.

Their work revealed that four genes, SAMD9L, HSD17B13, CUZD1, and VWA7, were lost sometime between 13 and 1 million years ago—long before humans and dingoes arrived in their habitats. These genes played important roles in immune function, tumor suppression, lactation, and the facilitation of a shift toward a hypercarnivorous diet and larger body size. All of these factors could potentially reduce the fitness of the thylacine to thrive in its environment.

The study also revealed decreased olfactory lobe size and a loss of olfactory receptor genes, suggesting a shift away from smell as a primary hunting sense. The study authors note that this may have been due to their larger size and changes in visual ability, making it easier for them to see prey over tall grasses or other obstacles.

The authors also note that these genetic changes may have been spurred by a climatic change that occurred prior to their genetic shifts.

"In line with temporal estimations of gene losses, our study provides an empirical case where we observe the coincidence in the timing of gene loss (approximately 13−6 Ma, following the Middle Miocene Climatic Transition (MMCT); approx. 15−13 Ma). This period marked significant ecological and climatic changes, during which Thylacinidae, previously small-bodied, unspecialized faunivores, underwent notable shifts such as an increase in size and developing adaptations to a hypercarnivorous diet, likely driven by the aridification of the Australian environment," they write.

While these changes were likely advantageous to the thylacine in the distant past, they may have ultimately facilitated its demise. The authors explain, "Although model-based population viability analyses suggest that the disease played only a minor role in thylacine extinction, other studies suggest that a 'canine-distemper-like' disease played a role in exacerbating its extinction. Therefore, adaptive ancestral gene loss may have provided specific advantages to the thylacine in response to environmental pressures during the MMCT, while being deleterious in the recent past."

This study highlights the importance of genetic changes in species survival and may extend into future conservation efforts. The authors say, "Similar investigations of other extant and extinct species can provide a more comprehensive understanding of their past ecologies and trait evolution, with potential implications for species survival and extinction. This research area remains underexplored in conservation genetics but will likely illuminate ancient evolutionary patterns and guide effective conservation strategies."

© 2025 Science X Network