I personally believe the answer to why Neanderthals extinct - which remains sort of a mystery - is an answer is multicausal. Multiple factors usually are responsible for such an event. And it's usually a story of "and..." instead of just. Likely, before the eventual demise there was already a declining population and diversity with increased stress due to a number of factors, including potential direct competition with homo sapiens, even if there's also evidence of some peaceful intermixing. I will not focus on those parts but on one specific part, but I have to stress out that I don't believe there's a single cause for the extinction of Neanderthals. Instead i'll focus on one of the factors that might've contributed to its extinction, specifically based on the environmental conditions around the time of its demise or when they disappear from the fossil record.
According to wikipedia, Neanderthals went extinct around 40.000 years ago, this might also be a bit earlier or a bit later. It is a rough estimate of when they went extinct.
Neanderthals (/niˈændərˌtɑːl, neɪ-, -ˌθɑːl/ nee-AN-də(r)-TAHL, nay-, -THAHL;[7] Homo neanderthalensis or H. sapiens neanderthalensis) are an extinct group of archaic humans (generally regarded as a distinct species, though some regard it as a subspecies of Homo sapiens) who lived in Eurasia until about 40,000 years ago
At the time, the Campi Flegrei had its largest eruption known to date which occured around that time, also quoting from Wikipedia
First Phlegraean Period. It is thought that the eruption of the Archiflegreo volcano occurred about 39,280 ± 110 years (older estimate ~37,000 years) ago, erupting about 200 km3 (48 cu mi) of magma (500 km3 (120 cu mi) bulk volume) to produce the Campanian Ignimbrite eruption. Its Volcanic Explosivity Index (VEI) was 7 and it left a large part of eastern Europe covered in ash.
"The dating of the Campanian Ignimbrite Eruption (CI) to ~37,000 calendar years B.P. draws attention to the coincidence of this volcanic catastrophe and the suite of coeval, Late Pleistocene biocultural changes that occurred within and outside the Mediterranean region. These included the Middle to Upper Paleolithic cultural transition and the replacement of Neanderthal populations by anatomically modern Homo sapiens, a subject of sustained debate. No less than 150 km3 of magma were extruded in this eruption (the CI eruption), traces of which can be detected in Greenland ice cores. As widespread discontinuities in archaeological sequences are observed at or after this eruption, a significant interference with ongoing human processes in Mediterranean Europe is hypothesized."
It is believed that the resulting ecological crisis wiped out both the last Neanderthal and the first Homo Sapiens populations of the early Upper Paleolithic. Modern humans then repopulated Europe from the east after the eruption and the ice age that took place from 38,000 to 36,000 BC.
Given the known extent of the Neanderthals
And the known extent of immediate aftermath of the eruption, with ash being found as far as Kazakhstan.
we can safely say there was an overlap with the immediate aftermath of the eruption.
If we look at a study that goes in depth about volcanic eruptions in the past 60.000 years based on the ice records in both Antarctica and Greenland, as well as the known climate fluctuations during the Last Ice Age, we can pinpoint better the extent of the eruption.
Magnitude, frequency and climate forcing of global volcanism during the last glacial period as seen in Greenland and Antarctic ice cores (60–9 ka)ka means kiloages and stands for thousand years ago, 1 ka is 1000 years ago.
Throughout the investigated period, we find that 69 volcanoes are larger than the Tambora 1815 CE eruption, and 1 unknown volcano occurring at 45.56 ka b2k in the NH and 1 unknown volcano at 38.13 ka b2k in low latitudes or in the Southern Hemisphere are larger than the Taupo, Oruanui, eruption occurring at 25.32 ka in present-day New Zealand. The Icelandic NAAZ II eruption (55.38 ka b2k) has by far left the largest sulfate deposition in Greenland, but due to its minor sulfate deposition in Antarctica, it is thought that only a fraction of the sulfur gases was injected into the stratosphere. In general, we observe significantly higher occurrences of very large eruptions (VEI-7 or larger) than estimated from the geological record, indicating that ice cores provide a more complete picture of volcanic activity in the past.
The study found evidence of 69 eruptions larger than the Mount Tambora eruption in 1815 that created the Year without a Summer over the past 60.000 years (approximately happening once on average every 1000 years). It also found 2 additional eruptions that were larger than the Oruanui eruption which happened 25.000 years ago and is classified as VEI 8 (a true supervolcanic eruption), with two unidentified sources. One volcanic eruption also has been found that was 15 times the size of Laki in Iceland, but would have been a different type of eruption due to it being more resembling a mini-flood basalt kind of eruption, which Iceland nowadays is mostly known for.
Right after the onset of GS-9 at 39.92 ka b2k there is another pair of large eruptions separated by some 46 years. These are number 14 (39 915 a b2k; −10.6 W m−2) and number 38 (39 869 a b2k; −8.8 W m−2) of the large eruptions listed in Table 2. Both eruptions have bipolar sulfate distributions suggesting a NH eruption. Because of their magnitude and their stratigraphic setting right at the onset of GS-9 these volcanic events are both possible candidates for the Italian Y-5 Campanian Ignimbrite eruption. There is no tephra evidence for this suggestion in the ice cores, but tephra from this eruption has been identified in the Black Sea in a very similar stratigraphic setting at the onset of GS-9, and the eruption is independently dated by to 39.9 ± 0.1 ka b2k (Giaccio et al., 2017).
One of areas of interests here is the following quote. The 14th and 38th largest eruptions of this ice record took place about 39.900 and 39.850 years ago, 50 years apart from each other, with some margin of error on the exact dating, both taking place in the Northern Hemisphere due to a bigger trace being found in Greenland than Antarctica. The study already presumes that one of those eruptions is the Campanian Ignimbrite eruption produced by Campi Flegrei in Italy, taking place at the onset of GS-9. Similarly, tephra also has been found in the stratigraphic record in the Black sea at the onset of GS-9.
GS means Greenland Stadial. And GS-9 means Greenland Stadial 9.
https://en.wikipedia.org/wiki/Stadial_and_interstadialSome explanation on stadials and interstadials but briefly said, stadials mean colder periods within an ice age while interstadials means milder periods in an ice age or glacial stage.
A glacial stage - unlike what most people associate it with - is by definition a period of time with major swings in climate, and an unstable climate with less balance than the interglacials we live in now. Most of our recent history is basically also a glacial stage as interglacials in comparison don't last that long compared to glacial stages. It's likely that without human intervention we would be entering a new ice age slowly but surely given Earth was already showing a downwarts trend prior to industrialization, characterized by the Little Ice Age and new ice build-up. Icelands largest glacier isn't a remnant of the last ice age but is only 4000 years old for instance. This is due to feedback effects and Milankovich cycles slowly again favouring an ice age, with seasons becoming less intense on the Northern Hemisphere, summers getting colder and winters getting milder but ice build-up is created by more remnant ice surving summer instead primarily which offsets possible milder temperatures during winter. Milder temperatures during winter also means more wetter conditions and therefore a milder set-up likely would still favour cold enough conditions for snowfall, meaning that milder winters in cold areas could translate into more snowfall. Build-up over years, decades and centuries could than due to positive feedback effects result in build-up if the cycles allow for it.
Despite human-made climate change we see more snowfall during autumn due to the milder conditions allowing for wetter conditions which in cold areas like Siberia or deep Canada still would translate into more snowfall paradoxically, sometimes used by climate sceptics to proof that the climate isn't warming, but snowfall isn't an indicator of global temperature. It is an indicator of precipitation.
When climate is colder, usually we see drier conditions because more of the available precipitable water would be frozen and not available in the water cycle. It is one of the reasons why Antarctica is so dry, even drier than the Sahara. The reality is very complex though.
Current Siberian heating is unprecedented during the past seven millenniaThe above linked study was done to notice the effects of modern climate change on Siberian summers, but to me more interesting was to indeed see the declining trend prior to industrialization. Also it basically suggests that the Year Without a Summer - which seems to visible here, might have been the coldest summer here in the past 7000 years. Truly a "year without a summer".
which i indicated here
Back to GS-9 which the earlier study i talked about and associates with the eruption of Campi Flegrei. GS-9 means Greenland Stadial 9 and basically correlates with the following colder period within the overall ice age.
GS-9 roughly correlating with the 9 even if the 9 here stands above the brief interglacial.
Basically there's correlation between this eruption and in addition another unidentified one taking place, both in the northern hemisphere which happened at the onset of a severing of the ice age conditions and climatic cooling.
While this itself alone cannot explain their extinction itself, it could've definitely contributed to it, if conditions were already not great to start with for them.
Warming & melting would occur later, the peak of the ice age (last glacial maximum) was yet to occur which took place around 25.000 years ago.
When a large eruption occurs it will have a short term impact on the climate, a volcanic winter or cooling for a couple of years to maybe a decade if it was large enough. But this is also would allow for more buildup - especially due to cooler summers - which means that when conditions return to normal, the new balance would be disturbed already and due to the positive feedback effects would trigger additional cooling by more initial surviving ice during the summer. This basically means that when conditions return to normal, the normal would already be cooler than the normal conditions prior to the event.
Also worth to note, while it is common knowledge that volcanic eruptions can have an impact on the global climate, less known it is that a changing climate can also have an impact on volcanoes.
Overall, the frequency of volcanic eruptions per millennium is rather constant throughout the investigated period and comparable to that of the most recent millennia. In agreement with previous studies, however, we find elevated levels of volcanic activity in the NH during the deglacial period (16–9 ka b2k). In particular, many very large eruptions occurred in this interval, quite likely associated with the redistribution of mass related to the meltdown of the major glacial ice sheets in this period.
Elevated volcanism was seen during deglaciation. This is a period of rapid change where ice melts quite quickly. Warming episodes at the end of a glacial stage are usually quite abrupt and also unstable by nature but happen relatively quickly.
It makes sense that elevated volcanism would occur due to several volcanoes being buried under a metres thick ice and glaciers, the removal of that much weight and pressure on top of a volcano would change its behaviour. As well as isostasy rebounding (the land that sinks due to the ice on top of it). And also due to sea level changes which might mean that some volcanoes would be buried under water during sea level rise or tower above sea during sea level drops. This is why human-made climate change can have this as consequences as well, in particular if we will be talking about the possible tipping point where the glaciers of Western Antarctica could melt, an area that is highly volcanologically active and contains a number of volcanoes buried under miles thick ice.
https://science.nasa.gov/earth/climate-change/fire-and-ice-why-volcanic-activity-is-not-melting-the-polar-ice-sheets/While the exact number of volcanoes in Antarctica is unknown, a recent study found 138 volcanoes in West Antarctica alone. Many of the active volcanoes are located in Marie Byrd Land. However, there’s no evidence of a dramatic volcanic eruption in Antarctica in the recent geologic past. Seroussi says details about the volcanism of many parts of Antarctica (particularly in East Antarctica) remain uncertain, both because they’re covered by ice and because their remoteness makes surveying them difficult.
