**Summary: Causes of Woolly Mammoth Extinction—Environmental Change and Human Activity**

The extinction of the woolly mammoth, which occurred thousands of years ago in the Late Pleistocene, is a classic example of how species can disappear due to a combination of natural environmental changes and emerging human pressures.

**Environmental Factors:**
1.

**Climate Change at the End of the Ice Age:** Around 17,000 years ago, much of regions like Alaska were covered in grassland, largely glacier-free and connected by the Bering Land Bridge to Siberia.

As the Ice Age ended, the climate rapidly warmed and the environment transformed.

These shifts led to a reduction in the extensive cold, dry, grassy steppes—the preferred habitat of the mammoths.

**Habitat Loss:** The warming climate caused grasslands to shrink as forests and wetlands expanded.

This reduced the mammoths’ food supply, as they were adapted to graze vast plains of grass.

Increasing warmth also led to ice melt and rising sea levels, severing migration routes such as the Bering Land Bridge.

**Water and Temperature Shifts:** Changes in global temperature altered ecosystems and affected availability of resources such as water and oxygen, further stressing large mammals like the mammoth.

**Human Activities:**
1.

**Early Human Hunting:** Archaeological evidence suggests that early humans hunted mammoths for meat and ivory.

While some debate remains about the relative impact of hunting, mammoth remains found with tool marks and in association with ancient camps indicate that humans targeted them effectively for sustenance and raw materials.

**Synergy of Factors:** No single factor alone explains the extinction.

Instead, it is likely that the environmental stress from rapid climate warming made mammoths more vulnerable, and intense hunting by increasingly skilled human populations delivered the final blow.

**Summary: Causes of Woolly Mammoth Extinction—Environmental Change and Human Activity**

The extinction of the woolly mammoth, which occurred thousands of years ago in the Late Pleistocene, is a classic example of how species can disappear due to a combination of natural environmental changes and emerging human pressures.

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In-Breeding Likely Didn't End the Last of the Mammoth Population

A study of the last likely surviving mammoth population shows that genetics from in-breeding likely did not lead to their demise.

By Paul Smaglik
Jun 27, 2024 6:20 PMJun 27, 2024 6:22 PM
Wrangel Island mammoth tusk (Credit: Love Dalén)

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It would seem obvious that rising sea levels that cut off the last population of woolly mammoths on Wrangel Island from the Siberian coast 10,000 years ago caused in-breeding, leading to their eventual extinction. But a new genetic analysis, reported in Cell, counters that claim.

That result was unexpected, since an earlier report indicated that the mammoth population likely built up harmful genetic mutations, according to Love Dalén, a scientist with the Centre for Palaeogenetics of Sweden, and one of the paper’s authors.

“I was fairly surprised both at how few the mammoths on Wrangel Island were in the beginning (less than 10 individuals), and that we did not find any evidence for an accumulation of highly deleterious mutations,” Dalén says. He calls the relative lack of harmful mutations surprising, because an earlier paper published in 2017 in PLOS Genetics predicted they may have played a factor.

Natural Selection and Genetic Drift

The genetic story of this population — which likely started from 8 individuals and grew to 200 to 300 mammoths over 6,000 years within 20 generations — is a bit more complicated. Two sometimes competing genetic factors were at play.

Natural selection tends to purge harmful variants, because offspring carrying them would be less likely to survive. But genetic drift works to preserve mutations across generations.

This effect tends to be stronger in smaller populations, so it would make sense that it would impact the Wrangel Island mammoths.

Read More: Rapid Evolution Changes Species in Real Time

What Made the Island Mammoths go Extinct?

Although it appears that these two genetic forces competed, it wasn’t necessarily a fair fight.

“Whereas genetic drift affects all deleterious mutations in the same way, natural selection will be stronger the more deleterious a mutation is,” says Dalén. “That way, natural selection is expected to remove the very deleterious mutations from the population, while genetic drift leads to an increase in slightly deleterious ones.”

Therefore, over time, the most harmful mutations were purged, while a bunch of relatively innocuous ones remained. So, if inbreeding didn’t do in the mammoths, what did?

“This leaves us with some other possibilities, such as a disease outbreak, some sort of tundra fire, or very short-term climatic perturbation, where the latter two could have ruined the plant growth for one or a few seasons, which could have had disastrous consequences for such a small population,” Dalén says.

Read More: How Do We Know When a Species Is Extinct?

Conservation of Today

Although the interplay between natural selection and genetic drift didn’t appear to wipe out the mammoths of yore, it still has implications for conservation efforts of today.

For example, conservationists wishing to preserve a species that has almost gone extinct, but has partially recovered, could look to the Wrangel Island mammoths. The implication is that moving a few individuals between two isolated populations could slow genetic drift.

The study’s authors have yet to analyze DNA from the most recent Wrangel Island mammoths. However, researchers have found fossils from the last 300 years of the mammoths’ existence and plan to analyze their genomes.

Read More: Scientists Are Trying to Save These Animals From Extinction

Article Sources

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.

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How did climate change affect mammoth' habitat?

How did humans contribute to the wooly mammoth extinction?

What environmental factors contributed to the wooly mammoth extinction?

from 300,000 years ago up until 10,000 years ago

When did the wooly mammoth mostly become extinct?

**Environmental Factors:**
1.

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Rapid Reductions In Greenhouse Gas Emissions Are Critical For Avoiding A Major Mass Extinction Of Ocean Species

As humanity's greenhouse gas emissions continue to warm the world's oceans, marine biodiversity could be on track to plummet within the next few centuries to levels not seen since the extinction of the dinosaurs, writes Morgan Kelly for Princeton University.

A new study by Princeton University researchers modeled future marine biodiversity under different projected greenhouse gas emissions scenarios, comparing the results with Earth’s big mass extinctions. They found that if emissions are not curbed, the extinction rate for marine species could double by around 2100.

The researchers combined existing data on marine species with models of climate change to predict how changes in habitat conditions will affect the survival of sea animals around the globe over the next few centuries. They then compared their model to the magnitude of past mass extinctions captured in the fossil record, especially to the End-Permian Extinction - Earth's deadliest extinction event so far. The fossil record shows that more than 250 million years ago volcanic gas emissions caused ocean temperatures to increase and oxygen availability to drop, leading to a mass extinction claiming more than 80 percent of Earth's marine species.

Water temperature and oxygen availability are two key factors that will change as the climate warms due to human activity.

Marine animals have physiological mechanisms that allow them to cope with environmental changes, but only up to a point. The researchers found that polar species are more likely to go globally extinct if climate warming occurs because they will have no suitable habitats to move to. Tropical marine species will likely fare better because they have traits that allow them to cope with the warm, low-oxygen waters of the tropics. As waters north and south of the tropics warm, these species may be able to migrate to newly suitable habitats. The equatorial ocean, however, is already so warm and low in oxygen that further increases in temperature - and an accompanying decrease in oxygen - might make it locally uninhabitable for many species.

Together with overfishing and pollution, climate change could so become the leading factor in the extinction of species. Tropical waters would experience the greatest loss of biodiversity, while polar species are at the highest risk of extinction, the authors reported.

"Extreme warming would lead to climate-driven extinctions that, near the end of the century, will rival all current human stressors combined," so the study's key result according to first author Justin Penn, a postdoctoral research associate in the Department of Geosciences.

The study found, however, that reversing greenhouse gas emissions could reduce the risk of extinction by more than 70 percent.

"The silver lining is that the future isn't written in stone," says Penn. "The extinction magnitude that we found depends strongly on how much carbon-dioxide we emit moving forward. There's still enough time to change the trajectory of carbon-dioxid emissions and prevent the magnitude of warming that would cause this mass extinction."

The paper, "Avoiding ocean mass extinction from climate warming," is published in the journal Science.

**Climate Change at the End of the Ice Age:** Around 17,000 years ago, much of regions like Alaska were covered in grassland, largely glacier-free and connected by the Bering Land Bridge to Siberia.

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During the last ice age, woolly mammoths were among the largest creatures to walk the North American landscape. Now, a team of American and Canadian researchers has discovered that the elephantine beasts took the “walking” part of their job description quite seriously.

Based on an analysis of a single tusk from an adult male woolly mammoth found in Alaska, the scientists determined that the animal journeyed about 70,000 kilometres over the course of its life – a trip equivalent to nearly twice around the world.

“The range is staggering. ... He definitely moved across a huge, huge area,” said Clement Bataille, an assistant professor of earth and environmental science at the University of Ottawa and a co-author on the study.

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Dr. Bataille said the high degree of mobility may have been part of the mammoth’s mating strategy. In comparison, African elephants can travel a lot, too, he added, and males typically depart from the groups they are born into once they reach sexual maturity.

However, Dr. Bataille and his colleagues note that the requirement for such a large range to roam in may have ultimately hastened the extinction of the species once the climate warmed and the shaggy grazers were hemmed in by shifting vegetation patterns. That, in turn, would have left them more vulnerable to predators, including human hunters.

The study began in 2018 when Matthew Wooller, director of the Stable Isotope Facility at the University of Alaska Fairbanks, invited Dr. Bataille and other colleagues to join an effort to extract information from a mammoth fossil discovered in 2010 on the north side of the Brooks mountain range, a few hundred kilometres from the Arctic Ocean. The fossil dates back 17,000 years, to a time when much of Alaska was a glacier-free grass plain connected to Siberia by the Bering land bridge.

The researchers nicknamed their specimen “Kik,” after a river system near the place where it was found.

Using the mammoth’s sliced-open tusk, they obtained detailed measurements of oxygen and strontium isotopes that were locked in the ivory material. The mammoth acquired the isotopes, which vary according to local geology, through the vegetation and water it consumed over the course of its life. As the tusks grew at the rate of about five to six centimetres each year, they recorded changes in isotope levels, which reveal when and how often the animal moved between locations with different geology.

The team also tested isotope levels in rodents that were gathered in different parts of Alaska as part of museum collections. That allowed them to match their mammoth isotope measurements to geographic locations. Finally, they used artificial intelligence software to reconstruct possible paths the mammoth may have taken, working backward from the location where it died at the age of 28.

The results suggest that Kik began its life in the Yukon River basin of central Alaska. As a juvenile it moved regularly in a north-south pattern, during a time when it was likely part of a herd, the researchers said. At about age 16 its movements transitioned to longer distance travel, often centred on certain core areas where it stayed for periods of time before setting out for new pastures.

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“It just takes off and goes on these 500- to 600-kilometre trips all at one time, going from one core area to the next,” Dr. Bataille said. The study found that some of the places where the mammoth lingered are frequented today by migrating herds of caribou.

Jeffrey Rasic, a study co-author and archaeologist with the U.S. National Parks Service based in Fairbanks, said the data suggest that Kik followed a predictable sequence of movements. If that was typical for Alaskan mammoths, it would have provided a huge incentive for hunters moving into the area from Asia to situate themselves in places where they could reliably expect to meet their quarry at certain times of the year, rather than pursuing them over a vast landscape.

“That would be an ideal set-up for intercepting a really big ticket meal item like a mammoth,” he said.

Vincent Lynch, an evolutionary biologist at the University at Buffalo who was not involved in the study, said that while it’s not surprising to find animals moving over great distances, it’s quite a different matter to show that it happened in a species that no longer exists.

“That’s the trick that makes this study interesting,” he said. “It helps us better reconstruct the behaviour and ecology of mammoths in a way that’s really remarkable for an extinct species.”

Dr. Lynch, who has studied the genetics of the last known population of woolly mammoths, which died out about 4,000 years ago, said it’s an open question whether large-scale movement was a disadvantage.

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“We tend to think that widely distributed species which are mobile ... might be better able to find new habitats should the environment change. But could mammoths find refuge in a world that was warming?” he said.

One obvious limitation of the study is that its conclusions depend entirely on the movements of a single individual. Dr. Bataille said that he and his colleagues plan to perform a similar analysis on a female mammoth specimen for comparison.

The team’s study was published Thursday in the journal Science.

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What environmental factors contributed to the wooly mammoth extinction?

As the Ice Age ended, the climate rapidly warmed and the environment transformed.

Title:

Content: AR6 and The Paleocene-Eocene Thermal Maximum

By Andy May

The PETM or Paleocene-Eocene Thermal Maximum was a warm period that began between 56.3 and 55.9 Ma (million years ago). The IPCC AR6 report (actually a draft, not a final edited report), released to the public on August 9, 2021, suggests that this warm period is similar to what is happening today and they expect to happen in the future (IPCC, 2021, pp. 2-82 & 5-14). During the PETM, it was very warm and average global surface temperatures probably peaked between 25.5°C and 26°C briefly, compared to a global surface temperature average of about 14.5°C today, as shown in Figure 1.

Today we have tens of thousands of daily temperature measurements around the world and can calculate a fairly accurate global average surface temperature. To construct a global average for the PETM we must rely on proxy temperatures, such as oxygen isotope ratios, Calcium/Magnesium ratios in fossil shells, and fossil membrane lipids that are sensitive to temperature like Tex86. Proxy temperature values are sparsely located and have a temporal resolution, 56 Ma, of thousands to hundreds of thousands of years. Thus, in terms of rate of temperature change, they are not comparable to today’s monthly global averages.

Before diving into the PETM, we will provide some geological perspective. According to Christopher Scotese, the highest global average temperature in the Phanerozoic (the age of complex shelled organisms, or the past 550 million years) was the Triassic hothouse event, following the end of the Karoo Ice Age, around 250-300 Ma. Global average surface temperatures peaked then at about 27.9°C.

The Late Cretaceous was the next warm period and global temperatures reached 24°C by 80 Ma. Around 65 Ma, the famous Chicxulub bolide impact occurred near the Yucatan Peninsula creating a 100 million megaton blast that ended the dinosaurs, except for birds. Global temperatures decreased rapidly to a minimum of around 12°C. This is a little colder than the last glacial maximum, so the animals that survived the blast got hit with the cold. This cold period was brief, perhaps only ten years, but very cold.

After recovering from the blast, the world returned to a global surface temperature of 22°C, just above its Phanerozoic average surface temperature of 20°C. Then, about nine million years later, the PETM warming occurred, it is labeled in Figure 1. In addition to the PETM, the EECO (Early-Eocene Climatic Optimum, mismarked in Scotese’s figure as EEOC), the MECO (Middle-Eocene Climatic Optimum), the EOT (Eocene-Oligocene Transition) Cooling, MMCO (Middle-Miocene Climatic Optimum), the LGM (last glacial maximum), and the preindustrial (Little Ice Age) temperature of 13.8° are identified in Figure 1. The current global average surface temperature of 14.5°C, and the possible “PAW” or projected anthropogenic global warming temperature of 19.8°C are also identified. Even if the most extreme projected anthropogenic warming occurs, it only takes Earth to its Phanerozoic average temperature of 20°C. This gives us an idea of just how historically, or geologically, cold it really is today.

Mixing proxy temperature resolutions of hundreds of thousands of years and modern instrumental temperature averages must be done with care. Scotese’s proxy temperatures are based on geological glacial signatures and estimated equator-to-pole temperature gradients. They are reasonable, but they have a temporal resolution of tens-of-millions of years. Given this resolution, we cannot compare past rates of warming, or cooling, to the past 170 years, the period with daily global thermometer coverage. His points do not have the temporal resolution or accuracy to allow for that.

The PETM

Near the beginning of the EECO, there was an abrupt, but geologically short (< ~200,000 years) period of extreme warming usually called the “PETM” (Scotese, 2015). The PETM is the warmest of several short, very warm periods or “hyperthermals” that occurred in the late Paleocene and early Eocene between 56 and 53 Ma.

The PETM hyperthermal may have caused Earth’s surface to warm to nearly 26°C (79°F) at its peak, nearly 12°C warmer than today. At this time, SSTs (sea surface temperatures) reached 33°C in the North Atlantic, near Denmark (Stokke, Jones, Tierney, Svensen, & Whiteside, 2020). The PETM latitude of Denmark was about 45°N, south of its present latitude of 55.6°N, see Figure 3 for its location at the time. The warming is contemporaneous with a small-scale marine extinction event. The high temperatures also occur at about the same time as a carbon isotopic excursion (CIE) event. This means the carbon-13 and carbon-12 ratio changed abruptly for a short time, geologically. The CIE suggests a flow of carbon compounds, enriched in carbon-12, into the ocean and atmosphere. Hydrocarbons are enriched in carbon-12 because plants prefer it over carbon-13, so the source could be hydrocarbons, such as methane clathrates. Clathrates are compounds in which molecules of one component, in this case methane, are trapped in another, like water. Methane clathrates are sometimes called methane hydrates.

Figure 2 shows the section studied by Stokke, et al. There is an unconformity below the section, but the PETM deposit is thought to be complete. Sedimentation was very rapid and the entire 24-meter PETM section was probably deposited in 100,000 years. NAIP (North Atlantic Igneous Province, see Figure 3) ash deposits within the PETM body are dated to 55.6 Ma. Contemporaneously ocean pH and deep-ocean oxygen levels lowered (anoxia) (IPCC, 2021, p 2-82).

It is only barely visible in Figure 2, but after the unconformity, and just prior to the PETM warming event, North Sea SSTs drop to 14.5°C, before rising rapidly to 33°C. Today’s global, area-weighted, average SST is about 18.3°C, using NOAA MIMOC and University of Hamburg multiyear ocean mixed layer temperature data. Today’s average North Sea SST is about 11°C according to Climate-Data.org, so the temperature of 14.5°C prior to the PETM is a little warmer than today. According to NOAA MIMOC data, the global average SST, in the mixed layer, at 45°N is about 10°C today.

NAIP volcanism was active during and before the PETM. Basalts, five kilometers thick, were emplaced on eastern Greenland and the Faroe Islands between 56 and 55.6 Ma. This pre-PETM volcanic episode would have generated sulfur compounds. The sulfur compounds (such as SO2 and SO3), when combined with water, generate sulfuric acid, which cooled the atmosphere and oceans, lowered ocean pH, and removed oxygen from both the atmosphere and oceans.

Francesca McInerney and Scott Wing have also written about the PETM (McInerney & Wing, 2011). They emphasize the global impact of the event. They believe that global surface temperature increased 5-8°C. While Stokke, et al. place the beginning of the PETM at 55.9 Ma, McInerney and Wing place it at 56.0 to 56.3 Ma. The time difference is not significant, given the dating uncertainty.

The data suggests that the PETM extinctions were quite limited and coincident with a large increase in mammalian species. Approximately 30-50% of benthic (bottom dwelling) foraminifera and dinoflagellates (microscopic marine animals) went extinct. The benthic foraminifera that went extinct were mostly from the middle to deeper depths in the oceans. Some speculate that the extinctions were due to greater corrosivity of deeper waters, lower oxygen levels, and/or higher temperatures (McInerney & Wing, 2011). Other benthic animals, such as ostracodes, living in the same environment as the foraminifera did not show the same loss in numbers. McInerney and Wing speculate that the extinctions were mostly due to higher temperatures, but this is unclear. Temperatures were higher at the surface and on land, yet life thrived in these environments at the time.

Oddly, while benthic forams did not do well during the PETM, McInerney and Wing report their planktonic (floating) cousins did very well, increasing in both size and diversity. Some planktonic species greatly increased their range and numbers during the PETM.

On land, new mammals, especially primates, evolved at this time and spread widely. The PETM and EECO saw a “burst of mammalian first appearances.” The period is sometimes called the “mammalian dispersal event” (McInerney & Wing, 2011). This burst of new mammalian first appearances is seen in both North America and Europe, and coincides with the onset of the PETM CIE.

Besides mammals, the PETM and EECO saw the evolution and dispersal of numerous new and existing species of turtles and lizards. Suggestions that the PETM was so warm it was deadly in the tropics are unlikely to be true “because terrestrial ﬂoras from the tropics become more rather than less diverse during the PETM” (McInerney & Wing, 2011).

During the PETM, temperatures increased 6 to 12°C and there was no polar ice. Palm trees grew in the Arctic, and Antarctica was covered in forests. Biological diversity greatly increased during the PETM, especially among terrestrial plants (McInerney & Wing, 2011). Some plant species appeared to disappear during the PETM but reappeared later, suggesting they did not extirpate, but were simply not preserved for a short time. Many species flourished and expanded into new areas. The first occurrence of mangrove palms dates to the PETM. Overall, nature blossomed when global temperatures were likely 12°C warmer than today.

The cause of the PETM is unknown. As mentioned above, Ella Stokke’s work suggests that the warm period and the extinctions are closely related to, and possibly caused by, contemporaneous North Atlantic Igneous Province (NAIP) volcanism. The volcanism could have caused oxygen deprivation in the Atlantic Ocean, especially in the deep Atlantic, causing the benthic foraminifera extinctions. The NAIP region and the Fur Island, Denmark, area studied by Stokke and her colleagues are shown in Figure 3. The Fur Island outcrops provide a fairly complete geological record spanning the Paleocene-Eocene boundary. The sediments include volcanic ash beds from NAIP, fossil-rich claystones, and shales with clear records of the carbon isotope excursion and the PETM event. They used the TEX86 temperature proxy to estimate SST. The NAIP emplacement was most active between 56 and 54 Ma during the opening of the North Atlantic.

Many theories for the warming have been proposed, including a sudden release of CO2 and methane, but the evidence is ambiguous. Initially it was speculated that volcanism caused the release of a large amount of methane clathrates, which then caused temperatures to rise.

A lot of carbon dioxide and methane certainly entered the atmosphere during this time. The main problem with the methane clathrate theory is that there were not enough of them to supply the necessary carbon (McInerney & Wing, 2011). Other possible sources of the excess carbon in the atmosphere and oceans at the time, enriched in carbon-12, are volcanism and contact metamorphism in the NAIP (Stokke, Jones, Tierney, Svensen, & Whiteside, 2020). McInerney and Wing prefer the theory that Antarctic peat and permafrost melted and were the source of the excess carbon-12.

While total atmospheric carbon did increase in the PETM, climate models have not been able to reproduce the large temperature increase with reasonable parameters. The CO2 estimates (see Figure 4) that we have from the period are far too low. Even if the atmosphere is assumed to contain 16 times the preindustrial concentration of CO2 (4,800 ppm) many times the level suggested by the fossil evidence shown in Figure 4, and the climate sensitivity is assumed to be 3°C/2xCO2 (McInerney & Wing, 2011), the CO2 forcing is still not enough to cause the warming observed in the sedimentary record (IPCC, 2021, 5-14). The abbreviation “°C/2xCO2” means the rise in temperature due to doubling the CO2 atmospheric concentration.

NASA claims their simulations can model the PETM temperature rise if they incorporate very high CO2 sensitivity. Jiang Zhu and colleagues successfully simulated the PETM with existing data, but their model suggests a climate sensitivity of 6.6°C/2xCO2, which is not reasonable (Zhu, Poulsen, & Tierney, 2019). The IPCC AR6 very likely range of sensitivity is 2°C to 5°C/2xCO2 (IPCC, 2021, pp. TS-58). In AR5, the IPCC is more explicit: “ECS is very unlikely greater than 6°C is an expert judgment informed by several lines of evidence.” (IPCC, 2013, p. 1111). AR5 follows with a list of the evidence why ECS is not greater than 6.

Between 55 and 56 Ma, there are 16 proxy estimates of CO2 levels (Beerling & Royer, 2011, S.I. Table 1). The 16 proxy samples represent seven unique sample times, which are plotted in Figure 4. According to a summary paper by David Beerling and Dana Royer in Nature Geoscience, the CO2 concentration was about 487 ppm (328-667 ppm) during the PETM event. The dating error for the samples is estimated to be ±500,000 years and the error in the CO2 estimates is ±235 ppm (Beerling & Royer, 2011). There are four methods of determining ancient CO2 atmospheric concentrations according to Beerling and Royer. The two terrestrial methods are the abundance of stomatal pores on fossil leaves and the carbon isotope composition of carbonates in fossil soils. Leaf stomata reduce in number when CO2 becomes abundant and gain in number when it is lower, as it is today.

The two marine methods are the carbon isotope composition of phytoplankton fossils and the boron isotope composition of fossil foraminifera. I refer you to Beerling and Royer’s paper and their references for the details of how these methods work. There is also a decent summary in AR6 (IPCC, 2021, 2-15). The general uncertainty in CO2 concentration estimates in the Eocene is nearly 100%, that is the actual value is between twice the most likely value and half of it.

Stokke’s Denmark SSTs are also plotted in Figure 4 for comparison. The CO2 estimates are somewhat lower than other PETM estimates and only slightly higher than today, but global average temperatures were 10-12°C higher.

Today we measure atmospheric CO2 continuously, many times a day, and each sample has a precise date and time. The data from 56 Ma is obviously not comparable to today. Beerling and Royer claim the highest CO2 level occurred 52 Ma, over four million years after the PETM, see Figure 5. They have two CO2 estimates from that time period: 1,868 ppm (1,092 – 3.501 ppm) and 659 ppm (439 – 878 ppm). Elevated CO2 levels existed from 54 to 32 Ma and average around 800 ppm. The lack of correlation between increasing CO2 and temperature from the period 52 to 57 Ma is easily seen in Figure 4.

During the PETM, we can be confident that CO2 levels were only slightly higher than today, not high enough to be a significant factor in the warming event, as acknowledged in AR6 (IPCC, 2021, p 5-14). We certainly do not have any idea about the rate of PETM warming or the rate of CO2 increase, relative to today, since the estimates are thousands to hundreds of thousands of years apart.

The IPCC wants to use the PETM as an example of what can happen today, but they admit low to medium confidence in the amount of carbon released during the PETM and their inferred increase in CO2 can only account for half the estimated warming during that time (IPCC, 2021, p. 5-14). They are also trying, without success so far, to model global temperatures in the PETM. Their models of the CO2 impact on climate in the PETM and other selected periods do not predict the warming observed, so one could reasonably conclude that this means the models are not working. But, in AR6, they conclude that it means the feedbacks to surface temperature are changing with surface temperature. Thus the feedbacks have feedbacks (IPCC, 2021, p. 7-78). They do not believe the models can be incorrect, they conclude that we simply need to introduce another factor. This is Karl Popper’s definition of pseudoscience, a hypothesis that cannot be falsified. The PETM is an interesting time in geological history, but the causes of the warming, the lower ocean pH, the limited ocean extinctions, and increasing mammalian diversity are unclear. One thing for sure, the PETM is not an analogue for today.

The bibliography can be downloaded here.

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What are the causes of the wooly mammoth extinction?

What aspects of climate change contributed to the wooly mammoth extinction?

What environmental factors contributed to the wooly mammoth extinction?

These shifts led to a reduction in the extensive cold, dry, grassy steppes—the preferred habitat of the mammoths.

According to most recent research, what is the primary cause of wooly mammoth extinction?

How did climate change affect mammoth' habitat?

What are the causes of the wooly mammoth extinction?

What aspects of climate change contributed to the wooly mammoth extinction?

What environmental factors contributed to the wooly mammoth extinction?

**Habitat Loss:** The warming climate caused grasslands to shrink as forests and wetlands expanded.

How did climate change affect mammoth' habitat?

shrank grassland
pastures becoming swampy

This reduced the mammoths’ food supply, as they were adapted to graze vast plains of grass.

According to most recent research, what is the primary cause of wooly mammoth extinction?

How did climate change affect mammoth' habitat?

shrank grassland
food sources disappearing
restricted habitat

What are the causes of the wooly mammoth extinction?

Increasing warmth also led to ice melt and rising sea levels, severing migration routes such as the Bering Land Bridge.

According to most recent research, what is the primary cause of wooly mammoth extinction?

How did climate change affect mammoth' habitat?

What are the causes of the wooly mammoth extinction?

What aspects of climate change contributed to the wooly mammoth extinction?

What environmental factors contributed to the wooly mammoth extinction?

**Water and Temperature Shifts:** Changes in global temperature altered ecosystems and affected availability of resources such as water and oxygen, further stressing large mammals like the mammoth.

According to most recent research, what is the primary cause of wooly mammoth extinction?

How did climate change affect mammoth' habitat?

What are the causes of the wooly mammoth extinction?

What aspects of climate change contributed to the wooly mammoth extinction?

What environmental factors contributed to the wooly mammoth extinction?

**Human Activities:**
1.

**Early Human Hunting:** Archaeological evidence suggests that early humans hunted mammoths for meat and ivory.

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Siberia's 'mammoth graveyard' reveals 800-year human interactions with woolly beasts

Woolly mammoths are evocative of a bygone era, when Earth was gripped within an Ice Age. Current knowledge places early mammoth ancestors in the Pliocene (2.58–5.33 million years ago, Ma) before their populations expanded in the Pleistocene (2.58 Ma–11,700 years ago, kyr). However, as climate changed, their numbers dwindled to isolated populations in modern Siberia and Alaska, until their last dated survival 4 kyr ago.

In the East Siberian Arctic (>70 °N), there is not only evidence of significant woolly mammoth populations, but also how humans interacted with them, the focus of new research in Quaternary Science Reviews.

Along the Berelekh River, Russia, a 'mammoth graveyard' can be found. Here, thousands of disarticulated bones, representing a minimum of 156 individual mammoths, found alongside an indicate the close proximity of these two communities, forming the Berelekh geoarchaeological complex.

Dr. Vladimir Pitulko, of the Russian Academy of Sciences, and colleagues aimed to assess the relationship between the 'mammoth graveyard' and the archaeological site through a re-examination of stratigraphic and paleogeographic data obtained in 2009, with new fieldwork focused on the left riverbanks where have readily yielded from their home in the sediment and appeared on the water's edge. Alongside them are remains of Pleistocene hare, Arctic fox and wolves, as well as soot and charcoal from hearths and worked mammoth tusks (one being an unfinished throwing spear).

The researchers suggest humans created these bone accumulations as a byproduct of the production of mammoth ivory technology, while hares may have been targeted for fur to produce winter clothing.

Notably, evidence of blowfly pupae activity on cavities in skulls and bones is indicative that the mammoth carcasses were added to the 'graveyard' de-fleshed. Indeed, there appears to be evidence of sorting of the bones, with only the most valuable transported to Berelekh from the area in which the mammoth was killed, leaving behind parts such as spinal columns, carpal ('hand') and tarsal ('foot') bones.

There are three radiocarbon dated peaks in woolly mammoth accumulation at 11.8, 12.2 and 12.4 kyr ago, which fall within known human settlement of the area (11.2–12.4 kyr ago) during the Bølling-Allerød deglacial, when the warmed and pollen evidence suggests the region became more arid.

Fluctuations in the abundance of mammoths in the 'graveyard' suggest human settlement of the area may also have changed through time (frequent occupation but not permanent), which the researchers attribute to on the floodplain permitting suitability for erecting campsites.

Radiocarbon dating of mammoth remains identifies their presence here pre-dating human settlement (beginning ~12.5 kyr ago), but also shows that humans remained in the area (until ~11.2 kyr ago) after mass mammoth remains accumulation declined (~11.8 kyr ago).

Given this, four possible causes are suggested by the scientists to explain such a significant mass accumulation of bones: 1) mass death by natural causes or human, 2) repeated group deaths in the same location, likely due to human predation, 3) concentration of remains by , such as river action, or 4) solely derived from human predation or scavenging from deceased carcasses.

However, the latter is considered to be the most likely to produce useful tools from ivory tusks, as well as meat to feed the community, as there is no evidence on the bones for a cause of mass death, radiocarbon ages do not cluster into multiple phases for recurrent death deposits and stream flows were unlikely to reach sufficient velocities to transport such heavy bones.

These findings are concurrent with mammoth remains at the Yana Paleolithic site, also in Siberia. Here, estimates suggest the 'graveyard' increased by 1–2 mammoths per year rather than a mass death event, a figure Dr. Pitulko and colleagues conclude could be similar or even higher for Berelekh.

This research is significant as it alters the previously-held belief that there was a lag of 50–80 years between mammoth bone accumulation from natural processes (such as deposition in flood channels) and , instead now defining a close relationship between the two over 700–800 years. Sadly, now that human-mammoth relationship has continued as ivory hunters have looted the site beyond further study.

More information: Vladimir V. Pitulko et al, From the Berelekh 'mammoth graveyard' to Berelekh geo-archaeological complex: Paleoenvironment, site formation processes, and human-mammoth relationships, Quaternary Science Reviews (2024). DOI: 10.1016/j.quascirev.2024.108692

Journal information: Quaternary Science Reviews

© 2024 Science X Network

Citation: Siberia's 'mammoth graveyard' reveals 800-year human interactions with woolly beasts (2024, June 10) retrieved 10 June 2024 from https://phys.org/news/2024-06-siberia-mammoth-graveyard-reveals-year.html
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How did humans contribute to the wooly mammoth extinction?

What are the causes of the wooly mammoth extinction?

While some debate remains about the relative impact of hunting, mammoth remains found with tool marks and in association with ancient camps indicate that humans targeted them effectively for sustenance and raw materials.

How did humans contribute to the wooly mammoth extinction?

What are the causes of the wooly mammoth extinction?

**Synergy of Factors:** No single factor alone explains the extinction.

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The Late Permian Mass Extinction Explained

Burning coal caused the largest mass extinction in earth’s history — the Late Permian Mass Extinction, or the Great Dying.

By Gabe AllenJul 22, 2022 10:00 AM
(Credit: Catmando/Shutterstock)

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Mass extinctions are evolutionary turning points — brief moments on a geologic time scale that drastically change the course of life on earth. One moment in particular stands out. The Permian-Triassic extinction, aka the Great Dying, eradicated more than 90 percent of earth’s marine species and 75 percent of terrestrial species 252 million years ago. It was the deadliest mass extinction event in the history of our planet, and its legacy lives on in the flora and fauna of the modern world.

The climactic and geochemical triggers for the Great Dying are unsettlingly similar to the effects of anthropogenic climate change. Global warming, ocean acidification and ozone layer-depletion caused ecological collapse.

The organisms that did recover from the extinction, did so slowly. Equatorial regions, which had been scorched beyond recognition, did not regain their characteristic biodiversity for five million years. Global ecosystems lacked both diversity and stability for at least eight million years following the event.

Survivors of the extinction event, though few, eventually repopulated the earth. These organisms are the ancestors of every living thing today. To paleontologists, the End-Permian Mass Extinction is the temporal boundary between the ancient paleozoic fauna and the modern fauna — a theoretical border between our world and a barely-recognizable predecessor.

Finding Precision

As recent as the late 2000s, the research community was significantly divided over what caused the Permian extinction. Some suggested that volcanism was at fault, while others suggested a meteor impact, like the one that wiped out the dinosaurs, caused the extinction.

Those that preferred the volcanic explanation, suspected the Siberian Traps, an expansive region of volcanic rock in present-day Siberia. The formation developed during an unrivaled period of volcanic rock on the ancient supercontinent Pangea.

“It’s the largest continental volcanic event and the largest mass extinction that we’re aware of on earth ever,” says Dr. Lindy Elkins-Tanton, a planetary scientist and professor at Arizona State University. “At the time, we didn’t know what caused either one or if they were definitively related to each other.”

In 2014, Chinese and American researchers made a breakthrough. The team extracted ancient volcanic ash from the Global Stratotype Section and Point for the early Triassic period, a site in Meishan, China that contains sediment that dates to the crisis unambiguously. By analyzing the uranium and lead isotopes contained in the ash, they put a relatively precise date on the extinction: 251.9 million years ago, give or take 70,000 years.

The next step was to date the Siberian Traps. Using the same method, the scientists analyzed samples from the site. “The bulk of this diffusive and explosive volcanism led up to the extinction,” says Elkins-Tanton, who was a part of the research team.

From these two dates, a timeline began to emerge. Intense volcanic activity on the ancient supercontinent of Pangea spewed magma through layers of basalt, coal and organic material. The combustion of these layers produced an immense amount of CO2 as well as other greenhouse gasses and chlorofluorocarbons.

Victims and Survivors

On land, both plants and animals perished in equatorial regions. At further latitudes, mosses and other lycopods began to dominate ecosystems that were once forested with conifers. Our ancestors, the tetrapods, died en masse. Survivors fled from the tropics towards the poles.

Like the mass extinctions before it, the End-Permian had an outsized impact on marine organisms. As CO2 from the atmosphere leached into the water, the ocean became more and more acidic. Simultaneously, high temperatures and cyanobacteria blooms consumed dissolved oxygen until there was little left.

Many organisms that had evolved to construct exoskeletons from minerals, found in ambient seawater, did not survive these changes in marine chemistry. The engineers of Permian reef ecosystems, rugose and tabulate corals, went completely extinct. Vast groups of externally-shelled cephalopods, ancestors of the nautilus, succumbed to the same fate. The End-Permian extinguished the last species of Trilobites as well, a group that had been on the decline since the Ordovician Mass Extinction.

Read more: The First Mass Extinction Event Explained: End-Ordovician

As with any mass-extinction, there were survivors of the Great Dying. Before the event, clam-like brachiopods were plentiful and diverse, but the extinction extinguished them in favor of their cousins, the bivalve mollusks. To this day, bivalves are widespread, while only a few orders of brachiopods remain.

Many researchers have speculated that the End-Permian may have catalyzed diversification among tetrapods. Though the extinction wiped many out permanently, the Early Triassic saw the creatures diversify and expand their ranges rapidly. This “radiation” eventually gave rise to archosaurs and later dinosaurs.

Drawing Parallels

The same factors that have driven anthropogenic global warming today drove global ecological collapse at the end of the Permian. An over-abundance of greenhouse gasses made the planet unlivable for most living organisms. Actually, the warming that initiated the End-Permian may have occurred at a much slower rate than anthropogenic global warming.

“It was the same climate change caused by the same greenhouse gasses as what we’re seeing today,” Elkins-Tanton says. “And it was almost the end of multicellular life on earth.”

However, climate scientists project that, if we can lower our emissions quickly enough, we can keep global warming to levels far below the ones that scorched the earth during the earth’s largest extinction event. It’s not too late to avoid total and complete ecological collapse.

“The rate of change might not have been as fast as today, but it changed the temperature so much that it’s really the worst-case scenario of what might happen,” David Bottjer says, paleoecologist and University of Southern California professor of earth sciences. “That’s why we should study it. To understand future scenarios for our climate.”

The future scenario, most-analogous to the End-Permian, would see humans continue to burn fossil fuels until few surviving organisms remained. It’s a scenario that may not represent the end of life on earth, but a fundamental change that would take millions of years to rebound from.

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Instead, it is likely that the environmental stress from rapid climate warming made mammoths more vulnerable, and intense hunting by increasingly skilled human populations delivered the final blow.

How did humans contribute to the wooly mammoth extinction?

What are the causes of the wooly mammoth extinction?

What aspects of climate change contributed to the wooly mammoth extinction?

What environmental factors contributed to the wooly mammoth extinction?