View source for Earth:Toba catastrophe theory

{{short description|Supereruption 74,000 years ago that may have caused a global volcanic winter}}
{{Infobox eruption
 | name = Toba eruption theory
 | photo = Image:Tobaeruption.png
 | photo-size =
 | caption = Artist's impression of the eruption from about {{convert|42|km|mi|abbr=on}} above northern Sumatra
 | date = c. 74,000 years [[Earth:Before Present|BP]]
 | volcano = [[Earth:Lake Toba|Toba Caldera Complex]]
 | type = Ultra-Plinian
 | location = Sumatra, Indonesia
 | coordinates = {{Coord|2.6845|98.8756|region:ID_type:event_scale:500000|display=inline,title}}
 | VEI = 8
 | map = Toba zoom.jpg
 | location-map =
 | map-size =
 | map-caption = [[Earth:Lake Toba|Lake Toba]] is the resulting [[Earth:Volcanic crater lake|crater lake]]
 | impact = Second-most recent supereruption; impact disputed
|deaths = (Potentially) almost all of humanity, leaving around 3,000–10,000 humans left on the planet
|end_time = 9–14 days
}}

The '''Toba eruption''' (sometimes called the '''Toba supereruption''' or the '''Youngest Toba eruption''') was a [[Earth:Supervolcano|supervolcano]] [[Earth:Types of volcanic eruptions|eruption]] that occurred around 74,000 years ago during the [[Earth:Late Pleistocene|Late Pleistocene]]<ref>{{cite news | url=https://www.haaretz.com/archaeology/2020-02-26/ty-article/.premium/no-toba-super-volcano-didnt-all-but-wipe-out-humans-74-000-years-ago/0000017f-e4ec-df2c-a1ff-fefdfc760000 | title=Surprisingly, Humanity Survived the Super-volcano 74,000 Years Ago | newspaper=Haaretz }}</ref> at the site of present-day [[Earth:Lake Toba|Lake Toba]] in Sumatra, Indonesia. It is one of the largest known explosive eruptions in the Earth's history. The '''Toba catastrophe theory''' holds that this event caused a severe global [[Earth:Volcanic winter|volcanic winter]] of six to ten years and contributed to a 1,000-year-long cooling episode, leading to a [[Biology:Population bottleneck|genetic bottleneck]] in [[Biology:Human|human]]s.{{sfn|Ambrose|1998}}<ref>Michael R. Rampino, Stanley H. Ambrose, 2000. "Volcanic winter in the Garden of Eden: The Toba supereruption and the late Pleistocene human population crash", Volcanic Hazards and Disasters in Human Antiquity, Floyd W. McCoy, Grant Heiken</ref>

A number of genetic studies have revealed that 50,000 years ago, the human ancestor population greatly expanded from only a few thousand individuals.<ref>A R Rogers, H Harpending, Population growth makes waves in the distribution of pairwise genetic differences., ''Molecular Biology and Evolution'', Volume 9, Issue 3, May 1992, Pages 552–569,</ref><ref>{{cite journal | doi=10.1111/j.1558-5646.1995.tb02297.x | title=Genetic Evidence for a Pleistocene Population Explosion | year=1995 | last1=Rogers | first1=Alan R. | journal=Evolution | volume=49 | issue=4 | pages=608–615 | pmid=28565146 | s2cid=29309837 }}</ref> Science journalist Ann Gibbons has posited that the low population size was caused by the Toba eruption.{{sfn|Gibbons|1993}} Geologist [[Biography:Michael R. Rampino|Michael R. Rampino]] of [[Organization:New York University|New York University]] and volcanologist Stephen Self of the [[Organization:University of Hawaiʻi at Mānoa|University of Hawaiʻi at Mānoa]] have supported her suggestion.<ref>{{Cite journal |last1=Rampino |first1=Michael R. |last2=Self |first2=Stephen |date=1993-12-24 |title=Bottleneck in Human Evolution and the Toba Eruption |url=https://www.science.org/doi/10.1126/science.8266085 |journal=Science |language=en |volume=262 |issue=5142 |pages=1955 |doi=10.1126/science.8266085 |pmid=8266085 |bibcode=1993Sci...262.1955R |issn=0036-8075}}</ref> In 1998, the bottleneck theory was further developed by anthropologist Stanley H. Ambrose of the [[Organization:University of Illinois Urbana-Champaign|University of Illinois Urbana-Champaign]].{{sfn|Ambrose|1998}} However, some physical evidence disputes the links with the millennium-long cold event and genetic bottleneck, and some consider the theory disproven.<ref>{{cite news |url=https://www.bbc.com/news/science-environment-22355515 |title=Toba super-volcano catastrophe idea 'dismissed' |date=30 April 2013 |publisher=BBC News |access-date=2017-01-08}}
* {{cite web|last=Choi |first=Charles Q. |url=http://www.livescience.com/29130-toba-supervolcano-effects.html |title=Toba Supervolcano Not to Blame for Humanity's Near-Extinction |website=Livescience.com |date=2013-04-29 |access-date=2017-01-08}}</ref><ref name=":1">{{cite journal |author1=Yost, Chad |display-authors=0 |date=March 2018 |title=Subdecadal phytolith and charcoal records from Lake Malawi, East Africa imply minimal effects on human evolution from the ~74 ka Toba supereruption |journal=Journal of Human Evolution |publisher=Elsevier |volume=116 |pages=75–94 |doi=10.1016/j.jhevol.2017.11.005 |pmid=29477183|doi-access=free }}</ref><ref>{{Cite journal |last1=Ge |first1=Yong |last2=Gao |first2=Xing |date=2020-09-10 |title=Understanding the overestimated impact of the Toba volcanic super-eruption on global environments and ancient hominins |url=https://www.sciencedirect.com/science/article/pii/S1040618220303335 |journal=Quaternary International |series=Current Research on Prehistoric Central Asia |language=en |volume=559 |pages=24–33 |doi=10.1016/j.quaint.2020.06.021 |bibcode=2020QuInt.559...24G |s2cid=225418492 |issn=1040-6182}}</ref><ref name=":2">{{cite web |last=Hawks |first=John |date=9 February 2018 |title=The so-called Toba bottleneck didn't happen |url=http://johnhawks.net/weblog/reviews/climate/toba-bottleneck-didnt-happen-2018.html |website=john hawks weblog}}</ref><ref>{{Cite journal |last1=Singh |first1=Ajab |last2=Srivastava |first2=Ashok K. |date=2022-06-01 |title=Had Youngest Toba Tuff (YTT, ca. 75 ka) eruption really destroyed living media explicitly in entire Southeast Asia or just a theoretical debate? An extensive review of its catastrophic event |journal=Journal of Asian Earth Sciences: X |volume=7 |pages=100083 |doi=10.1016/j.jaesx.2022.100083 |bibcode=2022JAESX...700083S |s2cid=246416256 |issn=2590-0560|doi-access=free }}</ref>

==Supervolcanic eruption==
The Toba eruption occurred at the present location of [[Earth:Lake Toba|Lake Toba]] in Indonesia and was dated (in 2012) to 73,880 ± 320 years ago through high-precision [[Physics:K–Ar dating|potassium–argon dating]].<ref>{{Cite journal |last1=Storey |first1=Michael |last2=Roberts |first2=Richard G. |last3=Saidin |first3=Mokhtar |date=2012-11-13 |title=Astronomically calibrated 40 Ar/ 39 Ar age for the Toba supereruption and global synchronization of late Quaternary records |journal=Proceedings of the National Academy of Sciences |language=en |volume=109 |issue=46 |pages=18684–18688 |doi=10.1073/pnas.1208178109 |issn=0027-8424 |pmc=3503200 |pmid=23112159|bibcode=2012PNAS..10918684S |doi-access=free }}</ref> This eruption was the last and largest of four eruptions of the Toba Caldera Complex during the [[Earth:Quaternary|Quaternary]] period, and is also recognized from its diagnostic horizon of ashfall, the Toba [[Earth:Tuff|tuff]].<ref>
* {{Harvnb|Chesner|others|1991}}, p. 200; {{Harvnb|Jones|2007}}, p. 174; {{Harvnb|Oppenheimer|2002}}, pp. 1593–1594; {{Harvnb|Ninkovich|others|1978}}
*  {{Harvnb|Rose|Chesner|1987}}, p. 913; {{Harvnb|Zielinski|others|1996}}.</ref> It had an estimated [[Earth:Volcanic explosivity index|volcanic explosivity index]] (VEI) of 8 (the highest rating on the scale); it made a sizable contribution to the {{cvt|100|×|35|km|adj=on}} [[Earth:Caldera|caldera]] complex.<ref>{{Harvnb|Oppenheimer|2002}}, p. 1593.</ref> 

Based on known distribution of ash fall and pyroclastic flows, eruptive volume was estimated to be at least {{cvt|2,800|km3}} [[Earth:Dense-rock equivalent|dense-rock equivalent]] (DRE), of which {{cvt|800|km3}} was deposited as ash fall.<ref>{{Harvnb|Jones|2007}}, p. 174; {{Harvnb|Rose|Chesner|1987}}, p. 913.</ref> Computational ash dispersal models suggested possibly as much as {{cvt|5300|km3}} DRE was erupted.<ref name="Costa">{{cite journal |first1=Antonio |last1=Costa |first2=Victoria C. |last2=Smith |first3=Giovanni |last3=Macedonio |first4=Naomi E. |last4=Matthews |date=2014 |title=The magnitude and impact of the Youngest Toba Tuff super-eruption |journal=Frontiers in Earth Science |volume=2 |page=16 |bibcode=2014FrEaS...2...16C |doi=10.3389/feart.2014.00016 |doi-access=free}}</ref> An even larger volume of {{cvt|6000|km3}} DRE has been suggested based on lost and eroded ash from pyroclastic flows.<ref>{{Cite journal |last1=Self |first1=S. |last2=Gouramanis |first2=C. |last3=Storey |first3=M. |date=2019-12-01 |title=The Young Toba Tuff (73.9 ka) Magma Body – True Size and the most Extensive and Voluminous Ignimbrite Yet Known? |journal=AGU Fall Meeting Abstracts |url=https://ui.adsabs.harvard.edu/abs/2019AGUFM.V51H0141S |volume=2019 |pages=V51H–0141|bibcode=2019AGUFM.V51H0141S }}</ref> The Toba eruption was the largest explosive volcanic eruption known in the Quaternary period.<ref name=Toba1978/>

The eruption was of exceptional intensity and was completed within only 9 to 14 days.<ref name=Toba1978>{{Cite journal |last1=Ninkovich |first1=D. |last2=Sparks |first2=R. S. J. |last3=Ledbetter |first3=M. T. |date=1978-09-01 |title=The exceptional magnitude and intensity of the Toba eruption, sumatra: An example of the use of deep-sea tephra layers as a geological tool |url=https://doi.org/10.1007/BF02597228 |journal=Bulletin Volcanologique |language=en |volume=41 |issue=3 |pages=286–298 |doi=10.1007/BF02597228 |bibcode=1978BVol...41..286N |s2cid=128626019 |issn=1432-0819}}</ref> Toba's erupted mass deposited an ash layer of about {{convert|15|cm|in|0}} thick over the [[Earth:Indian subcontinent|Indian subcontinent]]. A blanket of volcanic ash was also deposited over the [[Earth:Indian Ocean|Indian Ocean]], the Arabian Sea, and the South China Sea.<ref>{{Harvnb|Jones|2007}}, p. 173</ref> Glass shards from this eruption have also been discovered in [[Place:East Africa|East Africa]].<ref name=":3">{{cite journal |last1=Lane |first1=C. S. |last2=Chorn |first2=B. T. |last3=Johnson |first3=T. C. |date=2013 |title=Ash from the Toba supereruption in Lake Malawi shows no volcanic winter in East Africa at 75 ka |journal=Proceedings of the National Academy of Sciences |volume=110 |issue=20 |pages=8025–8029 |bibcode=2013PNAS..110.8025L |doi=10.1073/pnas.1301474110 |pmc=3657767 |pmid=23630269 |doi-access=free}}</ref>

==Climatic effects ==
By analyzing [[Earth:Proxy (climate)|climate proxies]] and [[Earth:Climate model|simulating climate forcing]], researchers can gain insights into the immediate climatic effects of the Toba eruption. However, there are limitations to both approaches. In sedimentary records where the Toba tuff does not serve as a [[Earth:Marker horizon|marker horizon]], it cannot pinpoint the exact section that records the environmental conditions immediately following the eruption. Meanwhile, in sedimentary records that do have the Toba tuff as a marker horizon, the [[Sedimentation|sedimentation rate]] may be too low to capture the short-term climatic effects of the eruption.{{sfn|Oppenheimer|2002}}<ref>{{Cite journal |last1=Huang |first1=Chi-Yue |last2=Zhao |first2=Meixun |last3=Wang |first3=Chia-Chun |last4=Wei |first4=Ganjian |date=2001-10-15 |title=Cooling of the South China Sea by the Toba Eruption and correlation with other climate proxies ~71,000 years ago |journal=Geophysical Research Letters |language=en |volume=28 |issue=20 |pages=3915–3918 |doi=10.1029/2000GL006113|bibcode=2001GeoRL..28.3915H |s2cid=128903263 |doi-access=free }}</ref> On the other hand, results of climate models entirely depend on the volatile budget of erupted magma, hence varies accordingly to the assumed volatile budget.

=== Climate proxy ===
Toba tephra layer in marine sediments coincides [[Biology:Δ18O|''δ''<sup>18</sup>O]] [[Physics:Marine isotope stages|marine isotope stage]] 5a to 4 boundary, marking a climatic transition from warm to cold caused by change in ocean circulation and drop in [[Earth:Carbon dioxide in Earth's atmosphere|atmospheric CO<sub>2</sub> concentration]], also known as [[Earth:Dansgaard–Oeschger event|Dansgaard-Oeschger event]]. Geologist [[Biography:Michael R. Rampino|Michael R. Rampino]] and volcanologist Stephen Self hypothesized that Toba eruption accelerated this shift.<ref>{{Cite journal |last1=Rampino |first1=Michael R. |last2=Self |first2=Stephen |date=1992-09-03 |title=Volcanic winter and accelerated glaciation following the Toba super-eruption |url=https://www.nature.com/articles/359050A0 |journal=Nature |language=en |volume=359 |issue=6390 |pages=50–52 |doi=10.1038/359050a0 |bibcode=1992Natur.359...50R |s2cid=4322781 |issn=1476-4687}}</ref><ref>{{Cite journal |last1=Rampino |first1=Michael R. |last2=Self |first2=Stephen |date=1993-11-01 |title=Climate-Volcanism Feedback and the Toba Eruption of ~74,000 Years Ago |url=https://www.sciencedirect.com/science/article/pii/S0033589483710811 |journal=Quaternary Research |language=en |volume=40 |issue=3 |pages=269–280 |doi=10.1006/qres.1993.1081 |bibcode=1993QuRes..40..269R |s2cid=129546088 |issn=0033-5894}}</ref> Testing this hypothesis required higher resolution sedimentary records.

Two marine sediment cores Toba marker horizon retrieved{{Clarify|reason=Is - Two marine sediment cores’ Toba-marker horizon, retrieved - meant, or - Two marine sediment cores of the Toba-marker horizon, retrieved -, or something else? For readers unfamiliar with something-marker horizons, a sequence of six words that seem to be nouns may be hard to parse.|date=December 2023}} from the [[Earth:Indian Ocean|Northern Indian Ocean]] and the South China Sea either showed no pronounced cooling or a {{cvt|0.8-1.0|C-change|F-change}} cooling in the centuries following eruption.<ref>{{Cite journal |last1=Huang |first1=Chi-Yue |last2=Zhao |first2=Meixun |last3=Wang |first3=Chia-Chun |last4=Wei |first4=Ganjian |date=2001-10-15 |title=Cooling of the South China Sea by the Toba Eruption and correlation with other climate proxies ~71,000 years ago |journal=Geophysical Research Letters |language=en |volume=28 |issue=20 |pages=3915–3918 |doi=10.1029/2000GL006113|bibcode=2001GeoRL..28.3915H |s2cid=128903263 |doi-access=free }}</ref><ref name=":4">{{Cite journal |last1=Schulz |first1=Hartmut |last2=Emeis |first2=Kay-Christian |last3=Erlenkeuser |first3=Helmut |last4=Rad |first4=Ulrich von |last5=Rolf |first5=Christian |date=2002 |title=The Toba Volcanic Event and Interstadial/Stadial Climates at the Marine Isotopic Stage 5 to 4 Transition in the Northern Indian Ocean |url=https://www.cambridge.org/core/journals/quaternary-research/article/abs/toba-volcanic-event-and-interstadialstadial-climates-at-the-marine-isotopic-stage-5-to-4-transition-in-the-northern-indian-ocean/471C87A8A3321E9CC3A40E4823268621 |journal=Quaternary Research |language=en |volume=57 |issue=1 |pages=22–31 |doi=10.1006/qres.2001.2291 |bibcode=2002QuRes..57...22S |s2cid=129838182 |issn=0033-5894}}</ref> The core resolution{{Clarify|reason=The antecedent in the previous sentence refers to two cores, so I expected either - The cores’ resolutions - or - The core resolutions -.|date=December 2023}} was insufficient to ascertain that the cooling was caused by the Toba eruption since the two events could be decades or centuries apart in the core.{{sfn|Oppenheimer|2002}} However, a severe cooling of only a few years is not expected to appear in these sediment records of centennial resolution.<ref name=":4" /> Nonetheless, the marine sedimentary records support that Toba had only a minor impact on the time scales longer than a century.<ref name=":4" />{{sfn|Oppenheimer|2002}}

In Greenland ice cores, a large sulfate spike that appeared between Dansgaard–Oeschger event 19 and 20 was possibly related to Toba eruption. The [[Biology:Δ18O|''δ''<sup>18</sup>O]] values of the ice cores indicate a 1,000-year cooling event immediately following the sulfate signal.<ref>{{Cite journal |last1=Zielinski |first1=G. A. |last2=Mayewski |first2=P. A. |last3=Meeker |first3=L. D. |last4=Whitlow |first4=S. |last5=Twickler |first5=M. S. |last6=Taylor |first6=K. |date=1996-04-15 |title=Potential atmospheric impact of the Toba Mega-Eruption ~71,000 years ago |url=http://doi.wiley.com/10.1029/96GL00706 |journal=Geophysical Research Letters |language=en |volume=23 |issue=8 |pages=837–840 |doi=10.1029/96GL00706|bibcode=1996GeoRL..23..837Z }}</ref> However, high-resolution [[Biology:Δ18O|''δ''<sup>18</sup>O]] excluded the possibility of a more-than-a-century-long cooling impact of the eruption and ruled out that Toba triggered the cooling as it was already underway.<ref name=":6">{{Cite journal |last1=Svensson |first1=A. |last2=Bigler |first2=M. |last3=Blunier |first3=T. |last4=Clausen |first4=H. B. |last5=Dahl-Jensen |first5=D. |last6=Fischer |first6=H. |last7=Fujita |first7=S. |last8=Goto-Azuma |first8=K. |last9=Johnsen |first9=S. J. |last10=Kawamura |first10=K. |last11=Kipfstuhl |first11=S. |last12=Kohno |first12=M. |last13=Parrenin |first13=F. |last14=Popp |first14=T. |last15=Rasmussen |first15=S. O. |date=2013-03-19 |title=Direct linking of Greenland and Antarctic ice cores at the Toba eruption (74 ka BP) |url=https://cp.copernicus.org/articles/9/749/2013/ |journal=Climate of the Past |language=English |volume=9 |issue=2 |pages=749–766 |doi=10.5194/cp-9-749-2013 |bibcode=2013CliPa...9..749S |s2cid=17741316 |issn=1814-9324|doi-access=free |hdl=2158/774798 |hdl-access=free }}</ref><ref name=":7">{{Cite journal |last1=Crick |first1=Laura |last2=Burke |first2=Andrea |last3=Hutchison |first3=William |last4=Kohno |first4=Mika |last5=Moore |first5=Kathryn A. |last6=Savarino |first6=Joel |last7=Doyle |first7=Emily A. |last8=Mahony |first8=Sue |last9=Kipfstuhl |first9=Sepp |last10=Rae |first10=James W. B. |last11=Steele |first11=Robert C. J. |last12=Sparks |first12=R. Stephen J. |last13=Wolff |first13=Eric W. |date=2021-10-18 |title=New insights into the ~ 74&thinsp;ka Toba eruption from sulfur isotopes of polar ice cores |url=https://cp.copernicus.org/articles/17/2119/2021/ |journal=Climate of the Past |language=English |volume=17 |issue=5 |pages=2119–2137 |doi=10.5194/cp-17-2119-2021 |bibcode=2021CliPa..17.2119C |s2cid=239203480 |issn=1814-9324|doi-access=free |hdl=10023/24161 |hdl-access=free }}</ref> 

Insufficient resolution in marine sediments bearing the Toba tuff has hindered the assessment of any short-term effects that may have lasted for less than a century.<ref name=":8">{{Cite journal |last1=Lane |first1=Christine S. |last2=Chorn |first2=Ben T. |last3=Johnson |first3=Thomas C. |date=2013-05-14 |title=Ash from the Toba supereruption in Lake Malawi shows no volcanic winter in East Africa at 75 ka |journal=Proceedings of the National Academy of Sciences |language=en |volume=110 |issue=20 |pages=8025–8029 |bibcode=2013PNAS..110.8025L |doi=10.1073/pnas.1301474110 |issn=0027-8424 |pmc=3657767 |pmid=23630269 |doi-access=free}}</ref>

In 2013, a microscopic layer of Toba ash was reported in sediments of Lake Malawi. Together with the high sedimentation rate of the lake and Toba marker horizon, several team have reconstructed the local environment after Toba eruption at subdecadal resolution of ~6–9 years. The sediments in core display no clear evidence of cooling and no unusual deviations in concentrations of climate-sensitive ecological indicators. These results imply that the duration of the Toba cooling must have been either shorter than the sampling resolution of ~6–9 years or too small in magnitude in East Africa.<ref name=":1" /><ref name=":8" /><ref>{{Cite journal |last1=Jackson |first1=Lily J. |last2=Stone |first2=Jeffery R. |last3=Cohen |first3=Andrew S. |last4=Yost |first4=Chad L. |date=2015-09-01 |title=High-resolution paleoecological records from Lake Malawi show no significant cooling associated with the Mount Toba supereruption at ca. 75 ka |url=https://pubs.geoscienceworld.org/geology/article/43/9/823-826/131970 |journal=Geology |language=en |volume=43 |issue=9 |pages=823–826 |doi=10.1130/G36917.1 |bibcode=2015Geo....43..823J |issn=0091-7613}}</ref><ref>{{Cite journal |last=Robock |first=Alan |date=2013-08-27 |title=The Latest on Volcanic Eruptions and Climate |url=http://doi.wiley.com/10.1002/2013EO350001 |journal=Eos, Transactions American Geophysical Union |language=en |volume=94 |issue=35 |pages=305–306 |doi=10.1002/2013EO350001|bibcode=2013EOSTr..94..305R }}</ref>

=== Climate model ===
The mass of sulfurous gases emitted during Toba eruption is a crucial parameter when modeling its climatic effects.

Assuming an emission of {{convert|1.7|e9t|e9ST|abbr=off|order=out}} of sulphur dioxide, which is 100 times the [[Earth:1991 eruption of Mount Pinatubo|1991 Pinatubo sulphur]], the modeled volcanic winter has maximum global mean cooling of {{cvt|-3.5|C-change|F-change}} and gradually returns within the range of natural variability 5 years after the eruption. An initiation of 1,000-year cold period or ice age is not supported by the model.<ref>{{Cite journal |last1=Timmreck |first1=Claudia |last2=Graf |first2=Hans-F. |last3=Zanchettin |first3=Davide |last4=Hagemann |first4=Stefan |last5=Kleinen |first5=Thomas |last6=Krüger |first6=Kirstin |date=2012-05-01 |title=Climate response to the Toba super-eruption: Regional changes |url=https://linkinghub.elsevier.com/retrieve/pii/S1040618211005817 |journal=Quaternary International |language=en |volume=258 |pages=30–44 |doi=10.1016/j.quaint.2011.10.008|bibcode=2012QuInt.258...30T }}</ref><ref>{{Cite journal |last1=Timmreck |first1=Claudia |last2=Graf |first2=Hans-F. |last3=Lorenz |first3=Stephan J. |last4=Niemeier |first4=Ulrike |last5=Zanchettin |first5=Davide |last6=Matei |first6=Daniela |last7=Jungclaus |first7=Johann H. |last8=Crowley |first8=Thomas J. |date=2010-12-22 |title=Aerosol size confines climate response to volcanic super-eruptions: AEROSOL SIZE CONFINES VOLCANIC SIGNAL |url=http://doi.wiley.com/10.1029/2010GL045464 |journal=Geophysical Research Letters |language=en |volume=37 |issue=24 |pages=n/a |doi=10.1029/2010GL045464|hdl=11858/00-001M-0000-0011-F70C-7 |s2cid=12790660 |hdl-access=free }}</ref> 

In a 2021 study, two other emission scenarios, {{convert|0.2|e9t|e9ST|abbr=off|order=out}} and {{convert|2|e9t|e9ST|abbr=off|order=out}} of sulphur dioxide which are 10 and 100 times of Pinatubo respectively, are investigated using state-of-art simulations provided by the [[Earth:Community Earth System Model|Community Earth System Model]]. Maximum global mean cooling is {{cvt|-2.3|C-change|F-change}} for a 0.2 billion tonnes SO<sub>2</sub> release and {{cvt|-4.1|C-change|F-change}} for a 2 billion tonnes SO<sub>2</sub> release. Negative temperature anomalies return to less than {{cvt|-1|C-change|F-change}} within 3 and 6 years for each emission scenario after the eruption.<ref>{{Cite journal |last1=Black |first1=Benjamin A. |last2=Lamarque |first2=Jean-François |last3=Marsh |first3=Daniel R. |last4=Schmidt |first4=Anja |last5=Bardeen |first5=Charles G. |date=2021-07-20 |title=Global climate disruption and regional climate shelters after the Toba supereruption |journal=Proceedings of the National Academy of Sciences |language=en |volume=118 |issue=29 |pages=e2013046118 |doi=10.1073/pnas.2013046118 |pmid=34230096 |pmc=8307270 |bibcode=2021PNAS..11813046B |issn=0027-8424|doi-access=free }}</ref>

Petrological studies of Toba magma constrained that the mass of [[Earth:Stratospheric sulfur aerosols|sulfuric acid aerosols]] from Toba eruption represents about 2–5 times the sulfuric acid aerosols generated during 1991 Pinatubo eruption.<ref name=":9">{{Cite journal |last1=Chesner |first1=Craig A. |last2=Luhr |first2=James F. |date=2010-11-30 |title=A melt inclusion study of the Toba Tuffs, Sumatra, Indonesia |url=https://linkinghub.elsevier.com/retrieve/pii/S0377027310001824 |journal=Journal of Volcanology and Geothermal Research |language=en |volume=197 |issue=1–4 |pages=259–278 |doi=10.1016/j.jvolgeores.2010.06.001|bibcode=2010JVGR..197..259C }}</ref><ref>{{Cite journal |last1=Scaillet |first1=Bruno |last2=Clemente |first2=Béatrice |last3=Evans |first3=Bernard W. |last4=Pichavant |first4=Michel |date=1998-10-10 |title=Redox control of sulfur degassing in silicic magmas |url=http://doi.wiley.com/10.1029/98JB02301 |journal=Journal of Geophysical Research: Solid Earth |language=en |volume=103 |issue=B10 |pages=23937–23949 |doi=10.1029/98JB02301|bibcode=1998JGR...10323937S |s2cid=30681359 }}</ref> The studies suggest that previous modelings of global temperature perturbations following Toba eruption were excessive.<ref name=":9" /> Ice core records of atmospheric sulfur injection during the period during which the Toba eruption occurred contain three large injections that are 10–30 times the Pinatubo sulfur.<ref name=":7" />

==Genetic bottleneck hypothesis==
===Genetic bottleneck in humans===

The Toba eruption has been linked to a genetic bottleneck in human evolution about 70,000 years ago;<ref>{{Harvnb|Gibbons|1993|p=27}}</ref><ref>{{Harvnb|Rampino|Self|1993a}}</ref> it is hypothesized that the eruption resulted in a severe reduction in the size of the total human population due to the effects of the eruption on the global climate.<ref>{{Harvnb|Ambrose|1998}}, ''passim''; {{Harvnb|Gibbons|1993}}, p. 27; {{Harvnb|McGuire|2007}}, pp. 127–128; {{Harvnb|Rampino|Ambrose|2000}}, pp. 78–80; {{Harvnb|Rampino|Self|1993b}}, pp. 1955.</ref> According to the genetic bottleneck theory, between 50,000 and 100,000 years ago, human populations sharply decreased to 3,000–10,000 surviving individuals.<ref>{{Harvnb|Ambrose|1998}}; {{Harvnb|Rampino|Ambrose|2000}}, pp. 71, 80.</ref><ref>{{cite web|url=http://www.bbc.co.uk/science/horizon/1999/supervolcanoes_script.shtml |title=Science & Nature – Horizon – Supervolcanoes |publisher=BBC.co.uk |access-date=2015-03-28}}</ref> It is supported by some genetic evidence suggesting that today's humans are descended from a very small population of between 1,000 and 10,000 breeding pairs that existed about 70,000 years ago.<ref><!-- name=a1998 -->{{cite news|url=http://news.bbc.co.uk/2/hi/science/nature/2975862.stm|title=When humans faced extinction|publisher=BBC|date=2003-06-09|access-date=2007-01-05}}</ref><ref>M.R Rampino and S.Self, ''Nature'' 359, 50 (1992)</ref>

Proponents of the genetic bottleneck theory (including Robock) suggest that the Toba eruption resulted in a global ecological disaster, including destruction of vegetation along with severe drought in the [[Earth:Tropical rainforest|tropical rainforest]] belt and in monsoonal regions. A 10-year volcanic winter triggered by the eruption could have largely destroyed the food sources of humans and caused a severe reduction in population sizes.<ref name="auto"><!-- name=robock2009 -->{{Harvnb|Robock|others|2009}}.</ref> These environmental changes may have generated population bottlenecks in many species, including hominids;<ref>{{Harvnb|Rampino|Ambrose|2000}}, p. 80.</ref> this in turn may have accelerated differentiation from within the smaller human population. Therefore, the genetic differences among modern humans may reflect changes within the last 70,000 years, rather than gradual differentiation over hundreds of thousands of years.<ref><!-- name=a1998 -->{{Harvnb|Ambrose|1998}}, pp. 623–651.</ref>

Other research has cast doubt on a link between the Toba Caldera Complex and a genetic bottleneck. For example, ancient [[Engineering:Stone tool|stone tool]]s at the Jurreru Valley in southern India were found above and below a thick layer of ash from the Toba eruption and were very similar across these layers, suggesting that the dust clouds from the eruption did not wipe out this local population.<ref>{{cite news |title=Mount Toba Eruption – Ancient Humans Unscathed, Study Claims |date=6 July 2007 |url=http://anthropology.net/2007/07/06/mount-toba-eruption-ancient-humans-unscathed-study-claims/ |website=Anthropology.net |access-date=2008-04-20 |archive-date=2008-01-11 |archive-url=https://web.archive.org/web/20080111031652/http://anthropology.net/2007/07/06/mount-toba-eruption-ancient-humans-unscathed-study-claims/ |url-status=dead }}</ref><ref>{{Cite journal |title=Super-eruption: no problem? |journal=Nature |date=July 2007 |first=Katherine |last=Sanderson |pages=news070702–15 |doi=10.1038/news070702-15 |s2cid=177216526 |url=http://www.nature.com/news/2007/070702/full/news070702-15.html |url-status=live |archive-url=https://web.archive.org/web/20081207012423/http://www.nature.com/news/2007/070702/full/news070702-15.html |archive-date=December 7, 2008}}</ref><ref>{{cite web |website=john hawks weblog |date=5 July 2007 |url=http://johnhawks.net/weblog/reviews/archaeology/middle/petraglia_toba_india_continuity_2007.html |title= At last, the death of the Toba bottleneck |author=John Hawks |author-link=John D. Hawks}}</ref> However, another site in India, the Middle Son Valley, exhibits evidence of a major population decline and it has been suggested that the abundant springs of the Jurreru Valley may have offered its inhabitants unique protection.<ref>Jones, Sacha. (2012). Local- and Regional-scale Impacts of the ~74 ka Toba Supervolcanic Eruption on Hominin Population and Habitats in India. Quaternary International 258: 100-118.</ref> Additional archaeological evidence from southern and northern India also suggests a lack of evidence for effects of the eruption on local populations, leading the authors of the study to conclude, "many forms of life survived the supereruption, contrary to other research which has suggested significant animal extinctions and genetic bottlenecks".<ref>See also {{cite web |url=http://anthropology.net/2010/02/25/newly-discovered-archaeological-sites-in-india-reveals-ancient-life-before-toba/ |title=Newly Discovered Archaeological Sites in India Reveals Ancient Life before Toba |date=25 February 2010 |website=Anthropology.net |access-date=28 February 2010 |archive-date=22 July 2011 |archive-url=https://web.archive.org/web/20110722183053/http://anthropology.net/2010/02/25/newly-discovered-archaeological-sites-in-india-reveals-ancient-life-before-toba/ |url-status=dead }}</ref> However, some researchers have questioned the techniques utilized to date artifacts to the period subsequent to the Toba supervolcano.<ref>National Geographic- Did early humans in India survive a supervolcano?</ref> The Toba Catastrophe also coincides with the disappearance of the [[Social:Skhul and Qafzeh hominins|Skhul and Qafzeh hominins]].<ref> Shea, John. (2008). Transitions or Turnovers? Climatically-forced Extinctions of Homo sapiens and Neanderthals in the East Mediterranean Levant. Quaternary Science Reviews 27: 2253-2270.</ref> Evidence from pollen analysis has suggested prolonged deforestation in South Asia, and some researchers have suggested that the Toba eruption may have forced humans to adopt new adaptive strategies, which may have permitted them to replace [[Biology:Neanderthal|Neanderthal]]s and "other archaic human species".<ref>{{cite news |title=Supervolcano Eruption In Sumatra Deforested India 73,000 Years ago |newspaper=ScienceDaily |date=24 November 2009 |url=https://www.sciencedaily.com/releases/2009/11/091123142739.htm}}</ref><ref><!-- name=williams2009 -->{{Harvnb|Williams|others|2009}}.</ref>

Additional caveats include difficulties in estimating the global and regional climatic impacts of the eruption and lack of conclusive evidence for the eruption preceding the bottleneck.<ref>{{Harvnb|Oppenheimer|2002}}, pp. 1605, 1606.</ref> Furthermore, genetic analysis of Alu sequences across the entire [[Biology:Human genome|human genome]] has shown that the effective human population size was less than 26,000 at 1.2 million years ago; possible explanations for the low population size of human ancestors may include repeated population bottlenecks or periodic replacement events from competing ''[[Biology:Homo|Homo]]'' subspecies.<ref>If these results are accurate, then, even before the emergence of ''Homo sapiens'' in Africa, ''Homo erectus'' population was unusually small when the species was spreading around the world. See {{Harvnb|Huff|others|2010}}, p.6; {{Harvnb|Gibbons|2010}}.</ref>

===Genetic bottlenecks in other mammals===
Some evidence points to genetic bottlenecks in other animals in the wake of the Toba eruption. The populations of the Eastern African [[Biology:Chimpanzee|chimpanzee]],<ref>{{Harvnb|Goldberg|1996}}</ref> [[Biology:Bornean orangutan|Bornean orangutan]],<ref>{{Harvnb|Steiper|2006}}</ref> central Indian [[Biology:Rhesus macaque|macaque]],<ref>{{Harvnb|Hernandez|others|2007}}</ref> [[Biology:Cheetah|cheetah]] and [[Biology:Tiger|tiger]],<ref>{{Harvnb|Luo|others|2004}}</ref> all recovered from very small populations around 70,000–55,000 years ago.

==Migration after Toba==
The exact geographic distribution of anatomically modern human populations at the time of the eruption is not known, and surviving populations may have lived in [[Earth:Africa|Africa]] and subsequently migrated to other parts of the world.  Analyses of [[Biology:Mitochondrial DNA|mitochondrial DNA]] have estimated that the [[Biology:Recent African origin of modern humans#Exodus from Africa|major migration from Africa]] occurred 60,000–70,000 years ago,<ref>{{cite web|title=New 'Molecular Clock' Aids Dating Of Human Migration History |url=https://www.sciencedaily.com/releases/2009/06/090604124023.htm |work=ScienceDaily |date=22 June 2009 |access-date=2009-06-30}}</ref> consistent with dating of the Toba eruption to around 75,000 years ago.{{Cn|date=May 2021}}

==See also==
* {{annotated link|Biology:Early human migrations}}
* {{annotated link|Biology:Most recent common ancestor}}
* {{annotated link|Earth:Quaternary extinction event}}
* {{annotated link|Biology:Recent African origin of modern humans}}
* {{annotated link|Earth:Timeline of volcanism on Earth}}

==Citations and notes==
{{Reflist|30em}}

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==Further reading==
* {{cite book |title=When Humans Nearly Vanished: The Catastrophic Explosion of the Toba Volcano |first=Donald R. |last=Prothero |year=2018 |publisher=Smithsonian Books |location=Washington |isbn=978-1588346353 |oclc=1020313538 }}

==External links==
* [http://www.jqjacobs.net/anthro/paleo/bottleneck.html Population Bottlenecks and Volcanic Winter]
* {{Cite web |url=http://www.andaman.org/BOOK/originals/Weber-Toba/textr.htm |title=Toba Volcano by George Weber |access-date=June 1, 2006 |archive-url=https://web.archive.org/web/20110422041006/http://www.andaman.org/BOOK/originals/Weber-Toba/textr.htm |archive-date=April 22, 2011 |url-status=dead |df=mdy-all }}
* [http://www.economist.com/surveys/displaystory.cfm?story_id=5299220&no_na_tran=1 "The proper study of mankind"] – Article in ''[[Finance:The Economist|The Economist]]''
* [http://www.anthro.illinois.edu/people/ambrose Homepage of Professor Stanley H. Ambrose], including bibliographic information on the two papers he has published on the Toba catastrophe theory
* [http://www.bradshawfoundation.com/stanley_ambrose.php Mount Toba: Late Pleistocene human population bottlenecks, volcanic winter, and differentiation of modern humans] by Professor Stanley H. Ambrose, Department of Anthropology, University Of Illinois, Urbana, USA; Extract from "Journal of Human Evolution" [1998] 34, 623–651
* [http://www.bradshawfoundation.com/journey/ Journey of Mankind] by The Bradshaw Foundation – includes discussion on Toba eruption, DNA and human migrations
* [https://www.sciencedaily.com/releases/2005/03/050310103042.htm Geography Predicts Human Genetic Diversity] ScienceDaily (Mar. 17, 2005) – By analyzing the relationship between the geographic location of current human populations in relation to East Africa and the genetic variability within these populations, researchers have found new evidence for an African origin of modern humans.
* [https://www.sciencedaily.com/releases/2007/02/070215134529.htm Out of Africa – Bacteria, As Well: Homo Sapiens And H. Pylori Jointly Spread Across The Globe] ScienceDaily (Feb. 16, 2007) – When man made his way out of Africa some 60,000 years ago to populate the world, he was not alone: He was accompanied by the bacterium Helicobacter pylori...; illus. migration map.
* [http://www.livescience.com/48545-toba-supervolcano-layered-sills-reservoir.html Magma 'Pancakes' May Have Fueled Toba Supervolcano]
* [https://www.youtube.com/watch?v=VM7Y1D8NMo8 Youtube video "Stone Age Apocalypse"]
{{DEFAULTSORT:Toba Catastrophe Theory}}
[[Category:Extinction events]]
[[Category:Geology theories]]
[[Category:Human evolution]]
[[Category:Supervolcanoes]]
[[Category:Pleistocene volcanism]]

{{Sourceattribution|Toba catastrophe theory}}