Category: Evolution

Climate Dynamics and the Decline of Elephants and Their Precursors

Biology, Climate Change, Evolution, Pre-History
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

Primate Facts

Anthropology/Archaeology, Biology, Evolution, Science

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

Clémence-Auguste Royer

Civil Rights, Evolution, Feminism, Quotes, Science, Secular Humanism

On this date in 1830, Clémence-Auguste Royer was born in Nantes, France. Her parents were Catholic royalists, and Royer’s early education took place in a convent school. Royer became a republican following the Revolution of 1848, and began to question other common views at that time. Royer obtained a teaching certificate and taught at girls schools in Wales, where she mastered English, and in France. She read widely on science in these school libraries. In 1855, as a result of her inquiries, she rejected Catholicism thoroughly, and devoted herself to science. She began to offer lectures on science and logic for women in Lausanne, Switzerland, in 1858. Royer translated Charles Darwin’s Origin of Species into French in 1863. She famously wrote a preface to the work which used Darwin’s mechanism for evolution as part of an anti-religious argument which Darwin himself did not make — by this time, the book was in its third English edition and contained several strong references to a creator. Royer had been an evolutionist before reading Darwin, having been strongly influenced by the writings of Jean Baptiste LaMarck. French scientists, especially atheists and anthropologists, were strongly influenced by evolution and natural selection as framed by Royer, who also discussed the implications of evolutionary theory for human beings and society in her introduction (it would be almost ten years before Darwin himself grappled with these issues in The Descent of Man). Royer continued as Darwin’s official French translator until the third French edition of Origin was published in 1870.

Royer, despite not being a research scientist, remained a popular interpreter of science as well as a philosopher of science throughout her life. As a woman, she was denied access to many learned societies, as well as university teaching positions. It has been argued by Jennifer Michael Hecht, among others, that Royer opened doors to women within the freethinking movement. Royer was a feminist who argued passionately for the rights of women, married and unmarried, to child custody, property, education and equality with men. In 1866, she had a son by her lover and life partner, Pascal Duprat, a married man, which sharpened her concern about the major legal obstacles then present to unwed mothers and their children. She published many books and articles throughout her life, and considered the pinnacle to be 1900’s Natura rerum, her theory of nature. In 1900, Royer was named a Chevalier of the Legion of Honor for her contributions as “a woman of letters and a scientific writer.” D. 1902

“Yes, I believe in revelation, but a permanent revelation of man to himself and by himself, a rational revelation that is nothing but the result of the progress of science and of the contemporary conscience, a revelation that is always only partial and relative and that is effectuated by the acquisition of new truths and even more by the elimination of ancient errors. We must also attest that the progress of truth gives us as much to forget as to learn, and we learn to negate and to doubt as often as to affirm.”
~ Clémence Royer, preface to Charles Darwin, L’origine des espèces, in Jennifer Michael Hecht, The End of the Soul

Charles Darwin’s Death

Biology, Evolution, Science, Scientist Profiles, Today in Science

Famed British biologist Charles Darwin died 139 years ago on April 19. Often dubbed as the “Father of Evolution,” Darwin provided the world with explanations on the origin and evolution of living things on Earth.

Darwin was born on Feb. 12, 1809, in Shrewsbury, England, and was homeschooled with his sister Caroline until the age of 8. He was sent to a boarding school after spending a year at a day school. His father enrolled him to the University of Edinburgh to study medicine. There, he began collecting, hunting, and naturalizing rather than studying medicine, according to Charles Darwin Online.

After graduating in 1831, Darwin accepted a job on the HMS Beagle, a vessel that mapped South America’s coast over a span of two or three years. During the job, he took notes and sent samples and specimens to botanist John Henslow in England. After returning to England after five years on the vessel, Darwin found that his specimen collection amazed Henslow and geologists, zoologists, and botanists.

Darwin’s research during his job on HMS Beagle contributed to the development of theory of evolution and natural selection. He, however, took over 20 years to publish the revolutionary theory — in 1858. He was apparently concerned about the acceptance of his idea. However, the theory turned out to be groundbreaking and was eventually widely accepted in mainstream science.

A few quotes:

“The mystery of the beginning of all things is insoluble by us; and I for one must be content to remain an agnostic.”

“We can allow satellites, planets, suns, universe, nay whole systems of universes, to be governed by laws, but the smallest insect, we wish to be created at once by special act.”

“False facts are highly injurious to the progress of science, for they often endure long; but false views, if supported by some evidence, do little harm, for every one takes a salutary pleasure in proving their falseness.”

“At some future period, not very distant as measured by centuries, the civilized races of man will almost certainly exterminate, and replace the savage races throughout the world.”

“A man who dares to waste one hour of his life has not discovered the value of life.”

“The highest possible stage in moral culture is when we recognize that we ought to control our thoughts.”

“It is a cursed evil to any man to become as absorbed in any subject as I am in mine.”

“A man’s friendships are one of the best measures of his worth.”

“A scientific man ought to have no wishes, no affections, – a mere heart of stone.”

“False facts are highly injurious to the progress of science, for they often endure long; but false views, if supported by some evidence, do little harm, for every one takes a salutary pleasure in proving their falseness.”

#CharlesDarwin #EvolutionByNaturalSelection #FatherOfEvolution

Clarence Darrow

Biology, Evolution, Science, Secular Humanism, U.S. History

On this date in 1857, Clarence Darrow, later dubbed “Attorney for the Damned” and “the Great Defender,” was born. For a time he lived in an Ohio home that had served as a stop on the Underground Railroad. His father was known as the “village infidel.” Darrow attended the University of Michigan Law School for one year, then passed the bar in 1878 and moved to Chicago. There he joined protests against the trumped-up charges against four radicals accused in the Haymarket Riot case. Darrow became corporate counsel to the City of Chicago, then counsel for the North Western Railway. He quit this lucrative post when he could no longer defend their treatment of injured workers, then went on to defend without pay Socialist striker Eugene V. Debs. In 1907, Darrow successfully defended labor activist “Big Bill” Haywood, charged with assassinating a former governor. His passionate denunciation of the death penalty prompted him to defend the famous killers, Loeb and Leopold, who received life sentences in 1924.

His most celebrated case was the Scopes Trial, defending teacher John Scopes in Dayton, Tenn., who was charged with the crime of teaching evolution in the public schools. Darrow’s brilliant cross-examination of prosecuting attorney William Jennings Bryan lives on in legal history. During the trial, Darrow said: “I do not consider it an insult, but rather a compliment to be called an agnostic. I do not pretend to know where many ignorant men are sure–that is all that agnosticism means.” Darrow wrote many freethought articles and edited a freethought collection. His two appealing autobiographies are The Story of My Life (1932), containing his plainspoken views on religion, and Farmington (1932). He also wrote Resist Not Evil (1902), An Eye for An Eye (1905), and Crime, Its Causes and Treatments (1925). His freethought writings are collected into Why I Am an Agnostic and Other Essays. He told The New York Times, “Religion is the belief in future life and in God. I don’t believe in either” (April 19, 1936). D. 1938.

“I don’t believe in God because I don’t believe in Mother Goose.”
~ Clarence Darrow, speech, Toronto, 1930.

Scopes Trial Evolution Speech

Biology, Evolution, Science

“If today you can take a thing like evolution and make it a crime to teach it in the public school, tomorrow you can make it a crime to teach it in the private schools, and the next year you can make it a crime to teach it to the hustings or in the church. At the next session you may ban books and the newspapers. Soon you may set Catholic against Protestant and Protestant against Protestant, and try to foist your own religion upon the minds of men. If you can do one you can do the other. Ignorance and fanaticism is ever busy and needs feeding. Always it is feeding and gloating for more. Today it is the public school teachers, tomorrow the private. The next day the preachers and the lectures, the magazines, the books, the newspapers. After a while, your honor, it is the setting of man against man and creed against creed until with flying banners and beating drums we are marching backward to the glorious ages of the sixteenth century when bigots lighted fagots to burn the men who dared to bring any intelligence and enlightenment and culture to the human mind.”
~ Clarence Darrow, “Scopes Trial” courtroom speech, July 13, 1925

What is evolution?

Biology, Evolution, Science

Yesterday was National STEM (Science, Technology, Engineering, and Math) Day!! So we’re going to cover a basic scientific concept that everyone should understand, but unfortunately many do not. The facts are most people who understand evolution accept it and most who don’t understand evolution strongly deny it. So lets get started with evolution 101:

What is evolution?

In biology, evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection.

The theory of evolution is based on the idea that all species? are related and gradually change over time.

Evolution relies on there being genetic variation? (This is differences in DNA. Variation between individuals in their DNA is what makes them different. ) in a population which affects the physical characteristics (phenotype) of an organism.

Some of these characteristics may give the individual an advantage over other individuals which they can then pass on to their offspring.

What is natural selection?

Charles Darwin’s theory of evolution states that evolution happens by natural selection.

Individuals in a species show variation in physical characteristics. This variation is because of differences in their genes?(Section of DNA within the genome that carries the information to make a molecule, usually a protein. They contain the instructions for our individual characteristics, like eye and hair colour. In humans and other complex organisms, genes are split into coding (exons) and non-coding sequences (introns). These split sections allow some genes to make more than one type of protein.

Individuals with characteristics best suited to their environment are more likely to survive, finding food, avoiding predators and resisting disease. These individuals are more likely to reproduce and pass their genes on to their children.

Individuals that are poorly adapted to their environment are less likely to survive and reproduce. Therefore their genes are less likely to be passed on to the next generation.

As a consequence those individuals most suited to their environment survive and, given enough time, the species will gradually evolve.

Different types of evolution:

Convergent evolution:

When the same adaptations evolve independently, under similar selection pressures.

For example, flying insects, birds and bats have all evolved the ability to fly, but independently of each other.

Co-evolution:

When two species or groups of species have evolved alongside each other where one adapts to changes in the other.

For example, flowering plants and pollinating insects such as bees.

Adaptive radiation:

When a species splits into a number of new forms when a change in the environment makes new resources available or creates new environmental challenges.

For example, finches on the Galapagos Islands have developed different shaped beaks to take advantage of the different kinds of food available on different islands. (See image)

Source: https://www.yourgenome.org

Image: Sketches of the heads of finches from the Galapagos Islands showing the differences in their beak shapes due to evolution.

Image credit: John Gould (14.Sep.1804 – 3.Feb.1881) – From “Voyage of the Beagle”