mamum is one of the most beloved ancient animals. The question of when they became extinct has been deeply troubled by paleontologists. Especially when their disappearance time seems to coincide with the time when humans arrive in North and South America, it adds a layer of mystery to this issue. This makes people wonder whether humans played a key role in the extinction of these huge wild beasts during the ice age more than 10,000 years ago.
Recently, paleontologists Joshua Miller and Carl Simpson published an article in Nature, refuting a latest timeline about mammoths that was also published in Nature in 2021.
In the 2021 study, an international team examined the remains of mammoths and the environmental DNA of more than 1,500 Arctic plants, and concluded that the "doomsday" of mammoths is much later than we originally thought. That study found that mammoths lived in Siberia until about 3,900 years ago, even thousands of years later than the conclusions drawn by the fossil record. It is believed that the wetter climate quickly turned the landscape from tundra to forest wetlands, resulting in the inability to support the survival of many large herbivores, causing the mammoth to eventually become extinct.
However, Miller and Simpson objected to this conclusion. They said that is used to establish an eDNA for the updated timeline, which is much more complicated than what academia has previously known . Because materials from different ages are often buried together, the sediments are very complex, so it is difficult to determine how old those eDNAs are.
Complex sediments
Researchers have many tools to determine the age of sediments and the materials contained therein. For example, researchers can perform radiocarbon dating on various things, including bones, teeth, charcoal, leaves, and so on. This is a very powerful method of measuring, but not everything can be accurately measured. For example, Currently, researchers still cannot use this method to independently determine the age of eDNA found in sediments.
DNA will fall off the organisms all the time. They may come from living organisms, or excrement. But in fact, even long after the animal dies, the DNA continues to shed, that is, it comes from the bones.
In some warm places, this will not bring any major problems to a given year. The bones may at most release DNA into the environment continuously over the decades of being broken down. However, in the Arctic and other cold places, something may take thousands of years to completely break down . Today, it is not uncommon to find 2,000-year-old reindeer antlers on the surface in some remote parts of the Arctic. In other words, in places where the decomposition process is quite slow, the genetic material of species that have died for a long time, or even extinct for a long time, can still continue to enter the surrounding sediments .
From recent discoveries, including the remains of mammoth cubs discovered in Canada not long ago, scientists have even realized that many ice age animals that died tens of thousands of years ago will become "mummys" in the dry and cold environment of the Arctic. They also give examples that the history of mummified remains of elephant seals near Antarctica may exceed 5,000 years. In this way, scientists cannot actually judge whether the eDNA stored in the sediment comes from living bodies or after death.
Miller believes that it is quite difficult to determine the age of ancient eDNA specimens. Shells can lie on the bottom of the sea for thousands of years. When you see shells on the beach, some may be shellfish that have died recently, while others may have died a thousand years ago. Similar examples also occur frequently in the records of vertebrates.
Questionable time span? The nearest mammoth fossil found in the Siberian region was buried in permafrost about 11,000 years ago. This is thousands of years earlier than the conclusion of eDNA analysis.
For Miller, this time difference is indeed too suspicious. Scientists have been searching for the remains of mammoth for so long, but have never been able to find any younger skeletons. However, the slow decomposition of animals in the Arctic can just explain such a huge time difference.
The original author also responded in the same periodical journal. They did not agree that the mammoth eDNA in the study sample may have been partly derived from cold, ancient weathered skeletons. They also pointed out that the youngest mammoth eDNA found showed a lower genetic diversity in , which is exactly what happens to the declining population at the end.
eDNA research pioneer Hendrik PoinarIn an interview, he said that Miller and Simpson's objections are indeed an effective point that needs further testing and analysis, but he believes that their analysis is not enough to counter multiple evidence that mammoths still existed in a later period.
For example, in the original study, the DNA evidence of also traced plants from that period. This suggests that environmental conditions allow mammoths to survive sustained due to the continuation of habitat in the tundra.
The impact of humans
For researchers, the key to the problem is still whether humans have had an impact on the global recession and extinction of mammoths and what impact will it have.
As we all know, our ancestors profoundly changed the landform with fire. They do hunt mammoths and make all kinds of items with their ivory. Therefore, to know the reason for the extinction of mammoths, you need to know the exact timeline of the disappearance of mammoths.
There are quite short intervals between the arrival and extinction of human beings in many places. But as more research emerges, some views may also be subverted. In some areas near the United States today, updated research has pushed back the time of human arrival, creating a larger time gap between human arrival and the extinction of mammoths and other giant faunas. These undoubtedly add complexity to the debate on the extinction mechanism . One of the biggest reasons why mammoths attract us is that they have lived with modern people and they have an interesting similarity to the animals that live around us today. For many, mammoths are typical of the giant fauna of ice age.
Imagine that thousands of years ago, these behemoths were walking on the earth, and our ancestors grew up under this situation. What an amazing and interesting scene. But we have completely missed them now.
Reference source:
https://www.uc.edu/news/articles/2022/11/uc-paleontologist-says-environmental-dna-paints-a-misleading-pi classic-of-mammoth-extinction.html
https://www.sciencenews.org/article/mammoths-extinct-earlier-edna-evidence
Picture: Thomas Quine, Flickr, CC BY
