“10 Beautiful Animals Driven to Extinction Since the Arrival of US”

“10 Beautiful Animals Driven to Extinction Since the Arrival of US”

As this is the penultimate post (since my course deadline is now looming…), I decided it would be good to reiterate one of the recurring themes in this blog series. This theme is humans. Though we focus on interglacial Europe, it is important to consider the ideas causing species extinction in a wider context. It has been clear through the discussion in this blog that humans have definitely played their part in affecting the movement and survival of species. For this reason, today I will give a brief summary of an article from The Telegraph and why I think it’s important.

The article emerged this December and gives a summary of 10 species supposedly driven to extinction by human activity. Some of these became extinct quite recently (e.g. the Western black rhinoceros), and others in the more distant past (e.g. Woolly mammoth). The former of these was only declared extinct in 2011, but this was solely the result of human exploitation. The article details other species (e.g. The great auk, the dodo and the Tasmanian tiger etc), which can be found in the link below (The Telegraph, 2016).

Dodo (left), Western black rhinoceros (right). Both extinct as a result of human activity.

(The Telegraph, 2016)

The point I wanted to make with this article is that humans have driven, and been solely responsible for an unknown number of extinctions throughout history. Therefore, their emergence in Europe, and its correlation with the disappearance of so many species suggests that human presence has been a key contributor to species disappearance well before the last few centuries.

I will leave you to dwell on those thoughts before my last blog post next week!!

Check out the article here:

http://www.telegraph.co.uk/travel/lists/beautiful-extinct-animals/

Thanks for the read, I definitely suggest checking out the article above! 

Extraterrestrial Non-Impact...

Extraterrestrial Impact Hypothesis: A Critique

Today we will briefly discuss an alternative theory for megafaunal extinctions in the late-Quaternary, which I have not previously mentioned. This is known as the extraterrestrial impact hypothesis. This impact apparently interrupted a period of warming with the onset of 1300 years of cooling climate known as the Younger Dryas (Daulton et al., 2016). 

Did the impact of a comet near the end of the Pleistocene cause Younger Dryas cooling and subsequent extinctions?

 

What does this hypothesis entail?

Firstly, this hypothesis contains several key parts:

• A comet (comets) hit the Earth 12,900 years ago.
• This impact forced Younger Dryas cooling.
• Sites from this time period possess a layer that contains: “magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with extraterrestrial helium” (Firestone et al., 2007 p. 16016). This indicates an extraterrestrial impact.
• This layer can be found at +50 sites across the US.
• Several comets may have hit the Laurentide Ice Sheet over North America, triggering destabilization and causing Younger Dryas cooling.
• This contributed to late-Pleistocene extinctions.
• Some megafaunal remains are radioactive near this time, in comparison to those from other time periods (Firestone et al., 2007).

Figure.1: Example of carbon spherules, found in 13 of the sampled sites.

(Firestone et al., 2007)

Evidence for no such impact

• An impact capable of damage to this extent would need to be >4km wide, no such evidence has been found of a crater this size (Firestone et al., 2007)
• There is evidence that some of the characteristics identified in the carbon rich layer or ‘impact layer’ may have been misinterpreted, and are not indicative of a collision. Lonsdalite and an increase in nanodiamond presence were used as evidence for impact, this is not found under re-examination (Daulton et al., 2016; Surovell et al., 2009).
• Impact-caused fires in the Arlington Canyon are often used as evidence for a comet. These fires are found to be natural and not induced by a collision (Scott et al., 2016).
• It is likely that even with an impact, effects would not have been large enough to have catastrophic effects on the megafauna. 

This hypothesis has now been largely put to rest. It’s more exciting to consider the idea of extraterrestrial impact as the cause of megafauna extinction, than it is to consider the much more robust science behind other explanations.

So as much as this is a cool picture…

(Source)

 …It has been pretty much discredited.

Cya next time! 

Is it getting hot in here?

Quaternary climate-driven megafaunal extinctions

It has been claimed that the Quaternary ice ages impacted species diversity, evolution and extinction (Lister, 2004; Davis and Shaw, 2001). Today, and throughout the past, it has been repeatedly proven that species respond to changes in climate. Both changes in the altitude of species, as well as latitudinal shifts in their range, are common responses to the warming and cooling of climate (Davis and Shaw, 2001). If an animal cannot adapt to these changes, it may become extinct. In the next 100 years there is predicted to be a major loss of species diversity (Cahill et al., 2012), therefore understanding how animals adjusted to climate change over past glacial cycles is particularly important in predicting how they will respond to anthropogenic climate change in the next century.

We can view this as:

 Climate Shift à Environmental Change (vegetation shift) à Species response (adaptive shift) à Survival/Extinction 

A Contemporary Context 

Today we can see all manner of animals adapting to climate change, even some of the smallest. For example, Argynnis paphia (Silver-washed fritillary) is a species of butterfly residing in Northern areas of Europe and Scandinavia. This is an insect adapted to cooler climates. Since 1970 there has been a poleward shift in the distribution of this butterfly, due to an increase in cold zone temperatures (fig.1) (Parmesan et al., 1999). After a certain length of time, this species may be pushed so far north, it will lose suitable habitat, and face becoming extinct. This could have been the case with many of the animals which have lived during the Quaternary period, which is why it is so important to understand past implications of climate  on ice age fauna.

Figure. 1: Argynnis paphia (Silver-washed fritillary) range in 1970 (blue) and shift in range by 1997 (green). 

(Parmesan et al., 1999  p. 582; UK Butterflies, 2016)

Quaternary Climate Change: Megafaunal Response

It has been suggested that many species underwent dramatic changes in their range in response to vegetation shifts brought about by  late-Quaternary climate (Stuart and Lister, 2007). Many of these may have caused extinction. Below is a compilation of selected late-Quaternary megafauna, including their estimated date of disappearance. 

Extinction Chronology 

Figure.2: A chronology of selected species affected by Quaternary climate change.

Compiled from: (Stuart and Lister, 2007)

Links to species and term definitions:

Stephanorhinus hemitoechus, Hippopotamus amphibious, Palaeoloxodon antiquus, Late Glacial, Eemian, Holocene, Last Glacial Maximum, Ursus spelaeus, Crocutacrocuta, Mammuthus primigenius, Coelodonta antiquitatis, herbivorous.

Top left: Crocuta crocuta. Top right: Ursus spelaeus. Bottom: Stephanorhinus hemitoechus.

Extinction Complexity

Prior to 21^st century research it was generally considered that most late-Quaternary extinctions occurred prior to the end of the Pleistocene epoch. It is now clear that this extinction was much more staggered than previously assumed, with many animals surviving into the Holocene (Stuart and Lister, 2007). Though, as we have discussed in previous posts, climate was by no means the only mechanism responsible for species extinction. Many of these animals were affected by changes in vegetation brought about by climatic deterioration or warming. This means that in a warming world there may be significant changes to current species distributions, including extinctions. 

Thanks for the read!

Case Studies from Europe

 ‘Impact of climatic changes in the Late Pleistocene on migrations and extinctions of mammals in Europe: four case studies’

(Baca et al., 2016)

This is just a quick summary of a very recent paper I thought was quite cool, as it covers both of the topics in this blog: extinction and migration of species. I found this particularly helpful as it discusses some of the species we have covered so far in this blog series, and others which we have not. These are:

Cave bear

Saiga antelope

Woolly mammoth

Collared lemming

The best way of envisioning the information in this article is by looking at the graph below. This shows radiocarbon dates, which have been converted into calendar dates (= years before present). This offers a really nice visualization of regional extinction and turnover events in Europe during the late-Quaternary. The authors conclude that the study of these four species offers a great perspective of the complexity of Quaternary faunal communities. Range shifts, regional extinction, and recolonisation events were common, and are normal phenomena in these species, rather than rare events.

Figure. 1: Species disappearance and turnover from radiocarbon (¹⁴C) dating over a 50,000y period mammoth top (2 clades), mammoth, cave bear, saiga antelope and collared lemming. Colours are indicative of different populations of the species.

(Baca et al., 2016 p. 18)

If this interests you feel free to read the paper: HERE

Another post coming soon!

Hunted to extinction?

Humans & Megafaunal Extinction (The Overkill Hypothesis)

Today is focused on understanding the true extent of hominin effect on European Quaternary megafauna. Beginning at around 50,000 years before present Eurasia lost over 35% of its mammal genera, many of these were living in Europe (Lorenzen et al., 2011). As discussed in the previous post, several questions surrounding hominin impacts will be addressed including: the evidence we have for humans hunting large animals, what these animals were used for, how much of an affect this had on faunal populations, and what differences there were between human (anatomically the same as modern humans since: around 150,000yrs ago) and Neanderthal exploitation of Quaternary fauna. For the purpose of this discussion it should be remembered that:

• 'Hominin' refers to both humans and Neanderthals.
• When 'human' is used we are talking about anatomically modern humans.
• When 'Neanderthal' is used we are talking about the extinct species Homo Neanderthalensis.
• In case you haven't heard of 'hominin', but only 'hominid' see: LINK

SO..

Just how common were scenes like this?

(Worall, 2016)

What evidence do we have that humans hunted megafauna?

There is some strong evidence for the effects of human hunting on megafauna. A few of these examples are:

• Human arrival in Europe corresponds well with the beginning of megafauna decline, the magnitude of animal disappearance was unprecedented. Many of them survived previous glacial cycles. The difference between those cycles and the last ice age was humans (Sandom et al., 2014).
• In modeled studies, Western Europe particularly has emerged as an extinction hotspot, and is closely timed with the arrival of humans, this follows with trends on other continents including: Australasia and South America (Sandom et al., 2014).
• As well as general correlations, there are numerous instances of human hunting at multiple European sites E.g: Poland and Austria, evidence for 'organised' mammoth hunts where animals were butchered at the kill site (Svoboda et al., 2005).
• Evidence found on the remains of animals resulting from human interaction and alteration. This includes: cut marks, burning and use of bones for a variety of other purposes (Karr, 2015).

 

Humans were certainly interested in Quaternary fauna, not just in hunting them but through social practices as depicted in this cave painting from: Chauvet Cave, France (~30,000 BC).

(Smithsonian, 2016)

What did humans use the animals they hunted for?

Some obvious and less obvious recorded uses of Quaternary fauna by their predators (humans and Neanderthals):

• Food (obviously)!

• There is evidence that mammoth bones were used as tools for butchery and building by Neanderthals (Demay et al., 2012).
  

• Use as cultural artifacts (Karr, 2015).
• Bone marrow extraction and exploitation (Karr et al., 2010).
  
  
  

Humans vs Neanderthals

There is significant debate surrounding the difference between human and Neanderthal diet (Yravedra and Cobo-Sanchez, 2015). Neanderthals are known to have exploited large and small animals alike in their diets, including: fish, rabbits, horses and elephants (Yravedra and Cobo-Sanchez, 2015; Smith, 2015). There is evidence from the Iberian Peninsula of Neanderthal hunting of hoofed animals, such as chamois. Typically, this is understood to be characteristic of human behavior (not Neanderthal). Likewise, Smith (2015) examined a site at La Cotte de St Brelade which preserves a record of Neanderthal behavior, there is evidence (tools, burnt material) that Neanderthals were exploiting mammoths, as well as woolly rhinoceros at this site. This is again not widely found as being characteristic of their behavior, so this hunting may be more opportunistic than a common feature of their diet. Yravedraand Cobo-Sanchez (2015) highlighted that there may be selective hunting of species, as sometimes chamois were not exploited even when their populations were large, indicating a level of complexity in Neanderthal hunting strategy. Still, there is evidence (from: isotopic analysis) that Neanderthals had high quantities of meat in their diet, meaning to some extent they may have contributed to faunal decline (Smith, 2015). Though, it must be highlighted that decline began around 50,000 years ago (Lorenzen et al., 2011), and Neanderthals became extinct around 40,000 years ago (Banks et al., 2008). This means Neanderthal contribution to fauna decline was likely small, and clearly short-lived in comparison to humans. Still, humans were better adapted to survive, while the Neanderthals disappeared...

...so just how much did our ancestors effect Quaternary megafauna...

?

Anatomically Modern Humans (AMH)

Homo Neanderthalensis

How much could this have reduced faunal populations?

This is the question. To what extent did humans reduce the populations of the fauna they hunted? In a global sense, there have been instances of modelled examples of the late-Quaternary megafaunal extinctions being entirely attributable to human hunting habits (Alroy, 2001). More up-to-date literature suggests that extinction is likely a combination of an interplay between humans and climate change (Bartlett et al., 2015). Though, the exact contribution fo humans to the loss of Quaternary megafauna is impossible to quantify.

  

 

(Source)

Nobody really knows for sure how much hunting may have reduced populations, but what we do know is that many species survived past ice ages. What was different this time?

People!

Thanks for reading!!