Huge mammals live harder, become extinct faster

Throughout the history of the earth, many species appear and disappear, replaced by new species capable of coping with a better life challenge. But some species last longer than others, while others extinct earlier or evolve faster.

Recently, a group of Finnish, Norwegian and American researchers have discovered that larger mammals seem to evolve faster than small species - but the underlying cause is not in size. Instead, scientists found that some smaller mammals were able to hibernate, dig, or hide in other shelters. In these ways, they overcome harsh environmental changes effectively.

However, large mammals suffer from difficult periods when food is scarce or the weather is extremely harsh. The large body makes it difficult for them to dig in or lower the rate of energy metabolism for extended periods of time. In other words, large body mammals face these factors as a brave adventurer, though they may not be able to overcome, and are forever changed because of this experience.

The finding - based on an analysis of the vast Neogene World fossil data - is somewhat surprising. At the individual level, the large mammal seems to live more clearly than the smaller species. For example, elephants can live up to 70 years while shrews live up to 2 years. Because the reproductive level is faster, small mammals should evolve faster, and small body mammals may appear and become extinct faster, but this is not the case.

Mammoth.(Photo: DailyMail)

Nils Stenseth, zoologist lecturer at the University of Oslo, told PhysOrg 'We believe the greatest importance of this work is to show that small mammals, contrary to expectations, do not evolve. faster than larger mammals, and some species actually evolve much slower. "

Previous studies - some focusing on tropical mammals - give different results in the rate of evolution based on the body size of fossil mammals, with the opposite outcome of the sample. and the results are no different. The possible explanation is that large body mammals in the tropics do not face harsh environmental conditions, so they exist longer and evolve more slowly. Moreover, small body mammals in the tropics may suffer from increasing competition resulting in faster turnaround rates.

However, in general, the ability to hibernate or enter a sleep state of small mammals seems to give them the greatest benefit of extending the lifespan of the species. According to the researchers' findings, 41/67 (61%) of extinct small mammal species are capable of hibernation while only 15/50 (30%) of large body mammals are available. This ability. And small mammals that do not hibernate have relatively faster evolutionary speeds, as they face many conditions.

The longest living species in this study are a mole, two slip squirrels, two squirrel species, which last for about 16 million years, and all are capable of digging or hibernating. Tapirs are the only large body mammal that evolves at a slow rate close to smaller body mammals. Most mammals do not hibernate evolve into new or extinct species in just a few million years.

The shortest survival time in researchers' data is 1 million years. However, Stenseth adds that organisms with really short lives do not have fossil data. He also explained that mammals that exist for a long time have their own advantages and disadvantages.

'The most diverse and crowded groups, such as mouse-like rodents, have high growth and extinction rates. But slower evolution groups like mice care for their own way and are very clever with what they're doing. '

In the current trend of weather crisis, this work can help scientists predict which species are more vulnerable to weather instability.

According to Mikael Fortelius, geology lecturer at the University of Helsinki and co-author of the project 'Large mammal species are being lost in recent times, and this trend is likely to continue. We are currently expanding our work to include surviving mammals and hope to present results soon. '