Climate Dynamics and the Decline of Elephants and Their Precursors

Elephants and their forebears were pushed into wipeout by waves of extreme global environmental change, rather than overhunting by early humans, according to new research.

The study, published in Nature Ecology & Evolution, challenges claims that early human hunters slaughtered prehistoric elephants, mammoths and mastodonts to extinction over millennia. Instead, its findings indicate the extinction of the last mammoths and mastodonts at the end of the last Ice Age marked the end of progressive climate-driven global decline among elephants over millions of years.

Although elephants today are restricted to just three endangered species in the African and Asian tropics, these are survivors of a once far more diverse and widespread group of giant herbivores, known as the proboscideans, which also include the now completely extinct mastodonts, stegodonts and deinotheres. Only 700,000 years ago, England was home to three types of elephants: two giant species of mammoths and the equally prodigious straight-tusked elephant.

An international group of palaeontologists from the universities of Alcalá, Bristol, and Helsinki, piloted the most detailed analysis to date on the rise and fall of elephants and their predecessors, which examined how 185 different species adapted, spanning 60 million years of evolution that began in North Africa. To probe into this rich evolutionary history, the team surveyed museum fossil collections across the globe, from London’s Natural History Museum to Moscow’s Paleontological Institute. By investigating traits such as body size, skull shape and the chewing surface of their teeth, the team discovered that all proboscideans fell within one of eight sets of adaptive strategies.

“Remarkably for 30 million years, the entire first half of proboscidean evolution, only two of the eight groups evolved,” said Dr Zhang Hanwen, study coauthor and Honorary Research Associate at the University of Bristol’s School of Earth Sciences.

“Most proboscideans over this time were nondescript herbivores ranging from the size of a pug to that of a boar. A few species got as big as a hippo, yet these lineages were evolutionary dead-ends. They all bore little resemblance to elephants.”

The course of proboscidean evolution changed dramatically some 20 million years ago, as the Afro-Arabian plate collided into the Eurasian continent. Arabia provided crucial migration corridor for the diversifying mastodont-grade species to explore new habitats in Eurasia, and then into North America via the Bering Land Bridge.

“The immediate impact of proboscidean dispersals beyond Africa was quantified for the very first time in our study,” said lead author Dr Juan Cantalapiedra, Senior Research Fellow at the University of Alcalá in Spain.

“Those archaic North African species were slow-evolving with little diversification, yet we calculated that once out of Africa proboscideans evolved 25 times faster, giving rise to a myriad of disparate forms, whose specialisations permitted niche partition between several proboscidean species in the same habitats. One case in point being the massive, flattened lower tusks of the ‘shovel-tuskers’. Such coexistence of giant herbivores was unlike anything in today’s ecosystems.”

By 3 million years ago the elephants and stegodonts of Africa and eastern Asia seemingly emerged victorious in this unremitting evolutionary ratchet. However, environmental disruption connected to the coming Ice Ages hit them hard, with surviving species forced to adapt to the new, more austere habitats. The most extreme example was the woolly mammoth, with thick, shaggy hair and big tusks for retrieving vegetation covered under thick snow.

The team’s analyses identified final proboscidean extinction peaks starting at around 2.4 million years ago, 160,000 and 75,000 years ago for Africa, Eurasia and the Americas, respectively.

“It is important to note that these ages do not demarcate the precise timing of extinctions, but rather indicate the points in time at which proboscideans on the respective continents became subject to higher extinction risk,” said Dr Cantalapiedra.

Unexpectedly, the results do not correlate with the expansion of early humans and their enhanced capabilities to hunt down megaherbivores.

Sources: University of Bristol

Ecofeminism

French feminist Françoise d’Eaubonne coined the term “ecofeminism” in 1974 for a new branch of feminism that focused on ecology, the study of the interactions between organisms and their environment. It holds that the domination and degradation of nature and the exploitation and oppression of women have significant connections.

Several environmental disasters in the US—most notably the 1979 near meltdown at the Three Mile Island nuclear power plant in Pennsylvania—brought 600 women together in 1980 for “Women and Life on Earth,” the first ecofeminist conference. Held in Massachusetts during the spring equinox, the conference explored the links between feminism, militarization, healing, and ecology. Ecofeminism was defined as a “women-identified movement” that sees Earth’s devastation and the threat of nuclear annihilation as feminist concerns because they are underpinned by the same “masculinist mentality” that oppresses women. Ecofeminism holds that women have a special role to play in protecting the environment and campaigning against damage to the planet.

As ecofeminism developed, it began to splinter into different approaches, one of which is sometimes described as cultural ecofeminism. This strand is rooted in spirituality, goddess worship, and nature-based religions. Its adherents, including American writer and activist Starhawk (Miriam Simos), argue that women have an intrinsic kinship with the natural environment, and, as instinctive carers, should be at the forefront of its protection. Other feminists criticize this approach for reinforcing gender stereotypes, claiming women’s moral superiority, and taking little account of class, race, or the economic exploitation of resources.

Sources: The Feminism Book (DK)

HMS Beagle First Voyage

It was on May 22, 1826, that HMS Beagle set out on its its first voyage. That was to Tierra del Fuego, and the captain, Pringle Stokes, got depressed and shot himself on the trip. The ship’s most famous voyage, with Captain Robert FitzRoy and Charles Darwin aboard, took place between 1831 and 1836. Curiously, FitzRoy also got depressed and committed suicide in 1865, cutting his throat with a razor.

Ancient Greeks and the Nature of Matter

The fundamental questions of what the world is made of, and where matter came from, are some of the oldest. In the 6th century BCE, Greek philosophers such as Thales and Anaximenes proposed that all substances were modifications of more intrinsic substances, the main candidates being water, air, earth, and fire. In the 5th century BCE, Empedocles claimed that everything was a mixture of all four of these substances, or elements. His near-contemporary Democritus developed the idea that the universe is made of an infinite number of indivisible particles called atoms. Finally, in the 4th century BCE the influential scholar Aristotle added a fifth element, ether, to Empedocles’four. Although Aristotle was skeptical of the idea of atoms, it is remarkable that the concepts of both atoms and elements had been proposed more than 2,000 years before either was proved to exist.

Primate Facts

A bit about our closest relatives:

Primate Facts —> Just how egocentric are human beings? Well, it’s telling that “primate,” the name employed for this order of mammals, is Latin for “first rank,” a not-so-subtle reminder that Homo sapiens considers itself the pinnacle of evolution. Scientifically speaking, though, there’s no reason to believe that monkeys, apes, tarsiers and lemurs–all of the animals in the primate order–are more advanced from an evolutionary perspective than birds, reptiles or even fish; they just happened to branch off in a different direction millions of years ago.

Until recently, naturalists divided primates into prosimians (lemurs, lorises and tarsiers) and simians (monkeys, apes and human beings). Today, though, the more widely accepted split is between “strepsirrhini” (wet-nosed) and “haplorhini” (dry-nosed) primates; the former includes all the non-tarsier promisimians, and the latter consists of tarsiers and simians. Simians themselves are divided into two major groups: old world monkeys and apes (“catarrhines,” meaning “narrow-nosed”) and new world monkeys (“platyrhines,” meaning “flat-nosed”). Technically, therefore, all human beings are haplorhine cattarrhines, dry-nosed, narrow-nosed primates. Confused yet?

#PrimateFacts #Science #Evolution

Chinese rocket tumbling uncontrolled back to Earth

A large segment of a Chinese rocket is expected to make an uncontrolled re-entry into the Earth’s atmosphere on the weekend, but Beijing has downplayed fears and said there is a very low risk of any damage.

A Long March-5B rocket launched the first module of China’s new space station into Earth’s orbit on April 29. Its 18-tonne main segment is now in freefall and experts have said it is difficult to say precisely where and when it will re-enter the atmosphere.

Re-entry is expected to be around 2300 GMT on Saturday, according to the Pentagon, with a window of nine hours either side.

Chinese authorities have said most of the rocket components would likely be destroyed on re-entry.

“The probability of causing harm… on the ground is extremely low,” Chinese foreign ministry spokesman Wang Wenbin told reporters on Friday.

Although there has been fevered speculation over exactly where the rocket—or parts of it—will land, there is a good chance any debris that does not burn up will just splash down into the ocean, given that the planet is 70 percent water.

“We’re hopeful that it will land in a place where it won’t harm anyone,” said Pentagon spokesman Mike Howard.

Howard said the United States was tracking the rocket segment but “its exact entry point into the Earth’s atmosphere cannot be pinpointed until within hours of its re-entry”.

Defense Secretary Lloyd Austin earlier said that the US military had no plans to shoot it down, and suggested that China had been negligent in letting it fall out of orbit.

“Given the size of the object, there will necessarily be big pieces left over,” said Florent Delefie, an astronomer at the Paris-PSL Observatory.

“The chances of debris landing on an inhabited zone are tiny, probably one in a million.”

In 2020, debris from another Long March rocket fell on villages in the Ivory Coast, causing structural damage but no injuries or deaths.

Jonathan McDowell, an astrophysicist at the Harvard–Smithsonian Center for Astrophysics, said that although there was no need to worry “too much”, the rocket’s design needed a re-think to stop such a scenario happening again.

“There is a real chance of damage to whatever it hits and the outside chance of a casualty,” he said.

“Having a ton of metal shards flying into the Earth at hundreds of kilometres per hour is not good practice, and China should redesign the Long-March 5B missions to avoid this.”

Sources: Phys.org