Did people or climate kill off the megafauna? Actually, it was both

10 12 2019

When freshwater dried up, so did many megafauna species.
Centre of Excellence for Australian Biodiversity and Heritage, Author provided

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Earth is now firmly in the grips of its sixth “mass extinction event”, and it’s mainly our fault. But the modern era is definitely not the first time humans have been implicated in the extinction of a wide range of species.

In fact, starting about 60,000 years ago, many of the world’s largest animals disappeared forever. These “megafauna” were first lost in Sahul, the supercontinent formed by Australia and New Guinea during periods of low sea level.

The causes of these extinctions have been debated for decades. Possible culprits include climate change, hunting or habitat modification by the ancestors of Aboriginal people, or a combination of the two.


Read more: What is a ‘mass extinction’ and are we in one now?


The main way to investigate this question is to build timelines of major events: when species went extinct, when people arrived, and when the climate changed. This approach relies on using dated fossils from extinct species to estimate when they went extinct, and archaeological evidence to determine when people arrived.


Read more: An incredible journey: the first people to arrive in Australia came in large numbers, and on purpose


Comparing these timelines allows us to deduce the likely windows of coexistence between megafauna and people.

We can also compare this window of coexistence to long-term models of climate variation, to see whether the extinctions coincided with or shortly followed abrupt climate shifts.

Data drought

One problem with this approach is the scarcity of reliable data due to the extreme rarity of a dead animal being fossilised, and the low probability of archaeological evidence being preserved in Australia’s harsh conditions. Read the rest of this entry »





Climate change and humans together pushed Australia’s biggest beasts to extinction

25 11 2019

people-megafaunaOver the last 60,000 years, many of the world’s largest species disappeared forever. Some of the largest that we generally call ‘megafauna’ were first lost in Sahul — the super-continent formed by the connection of Australia and New Guinea during periods of low sea level. The causes of these extinctions have been heavily debated for decades within the scientific community.

Three potential drivers of these extinctions have been suggested. The first is climate change that assumes an increase in arid conditions that eventually became lethal to megafauna. The second proposed mechanism is that the early ancestors of Aboriginal people who either hunted megafauna species to extinction, or modified ecosystems to put the largest species at a disadvantage. The third and most nuanced proposed driver of extinction is the combination of the first two.

The primary scientific tools we scientists use to determine which of these proposed causes of extinction have the most support are dated fossil records from the extinct species themselves, as well as archaeological evidence from early Aboriginal people. Traditionally, the main way we use these data is to construct a timeline of when the last fossil of a species was preserved, and compare this to evidence indicating when people arrived. We can also reconstruct climate patterns back tens of thousands of years using models similar to the ones used today to predict future climates. Based on the comparison of all of these different timelines, we conclude that abrupt climate changes in the past were influential if they occurred at or immediately before a recorded extinction event. On the other hand, if megafauna extinctions occur immediately after humans are thought to have arrived, we attribute more weight to human arrival as a driver.

Read the rest of this entry »





Being empathetic for better interdisciplinarity

4 06 2019

Source: taazatadka.com(originally published on the GE.blog)

Scientists appear to have mixed feelings when it comes to interdisciplinarity in science — the reaction spans from genuine enthusiasm right through to pure disdain.

I myself have crossed many research fields since my Masters project, but despite the support of my supervisors, I have already had to face some tough gatekeeping from science specialists in conferences and in front of other panels. Several times I was taken aback by some reactions, so I have started to become interested in the topic from a more analytical perspective. How are these fields’ boundaries defined in science?

Although each field’s specific methodology, jargon, and tendency to interpret results could represent communication barriers among them, this can be easily overcome by spending time learning the language of other groups, in the company of specialist collaborators, or by attending workshops.

But what about ideology — a philosophy of science inherent to a specific group of individuals? This is one of the things making us human. It definitely affects our society, and even if it is never assumed, it also affects the generation of scientific knowledge from its production to its transmission. Scientists have that connection to their field, its history, its identity, and its compromises.

For example, historians or philosophers use different ways of thinking than do physicists or biologists. The first group aims to clarify and analyse the reconstruction of past events, while the second group strives for conceptual understanding. While useful withina field, these specific ways of seeing science can generate roadblocks when two fields need to start a conversation.

I will tell you a story based on my own experience. Read the rest of this entry »





Legacy of human migration on the diversity of languages in the Americas

12 09 2018

quechua-foto-ale-glogsterThis might seem a little left-of-centre for CB.com subject matter, but hang in there, this does have some pretty important conservation implications.

In our quest to be as transdisciplinary as possible, I’ve team up with a few people outside my discipline to put together a PhD modelling project that could really help us understand how human colonisation shaped not only ancient ecosystems, but also our own ancient cultures.

Thanks largely to the efforts of Dr Frédérik Saltré here in the Global Ecology Laboratory, at Flinders University, and in collaboration with Dr Bastien Llamas (Australian Centre for Ancient DNA), Joshua Birchall (Museu Paraense Emílio Goeldi, Brazil), and Lars Fehren-Schmitz (University of California at Santa Cruz, USA), I think the student could break down a few disciplinary boundaries here and provide real insights into the causes and consequences of human expansion into novel environments.

Interested? See below for more details?

Languages are ‘documents of history’ and historical linguists have developed comparative methods to infer patterns of human prehistory and cultural evolution. The Americas present a more substantive diversity of indigenous language stock than any other continent; however, whether such a diversity arose from initial human migration pathways across the continent is still unknown, because the primary proxy used (i.e., archaeological evidence) to study modern human migration is both too incomplete and biased to inform any regional inference of colonisation trajectories. Read the rest of this entry »