Early reptile evolution, video


This 25 August 2019 video is called Evolution of Early Reptiles.

Barn swallows evolved alongside humans


This 2012 video from the USA says about itself:

This 3 1/2 minute film is the documentation of five baby Barn Swallows, their rapid growth, and departure from their nest.

They certainly kept their beautiful parents busy trying to feed them all.

There are many Barn Swallow nests all over our area in southern New Mexico, under the eaves of coffee shops, barns, carports, schools. This is our carport which seems to work well for them, protected from other animals, under cover, aerated, yet accessible. This is shot with a Canon 5DII using mostly a 70-200 mm lens.

From the University of Colorado at Boulder in the USA:

Barn swallows may indeed have evolved alongside humans

As humans evolved and expanded, so too did barn swallows

November 1, 2018

The evolution of barn swallows, a bird ubiquitous to bridges and sheds around the world, might be even more closely tied to humans than previously thought, according to new study from the University of Colorado Boulder.

The research, published this week in Molecular Ecology, offers preliminary insight suggesting that the barn swallow and its subspecies evolved alongside — but independently from — humans. These new results make it one of the only known species, in addition to microscopic organisms like bacteria or viruses, to have developed in such a way, upending previous assumptions that barn swallows evolved prior to human settlement.

“Humans could be a really big part of the story”, said Rebecca Safran, a co-author of the study and an ecology and evolutionary biology (EBIO) associate professor at CU Boulder. “There’s very few studies that can point to the exact influence of humans, and so here, this coincidence of human expansion and permanent settlement and the expansion of a group that relies really, really heavily on humans is compelling.”

Barn swallows are found across the northern hemisphere and are characterized by their mud-cup nests that are built nearly exclusively on human-made structures. Despite their prevalence, however, not much is known about their evolutionary history, the timing of their expansion from northern Africa (where they originated) or how the six subspecies evolved so physically and behaviorally different yet remain almost genetically identical.

Previous studies published in the Proceedings of the Royal Society of London and Molecular Phylogenetics and Evolution looked into these questions and found that the different subspecies split early, well before human settlement.

This new study, however, gave the topic a fresh look by examining the whole genome of 168 barn swallows from the two sub-species farthest apart on an evolutionary scale: H. r. savignii in Egypt (a non-migratory species that lives along the Nile) and H. r. erythrogaster in North America (a species found throughout North America that migrates seasonally to South America).

These data — which are on the order of 100,000 times bigger than the previous dataset used — were then analyzed with more sophisticated computational resources and methods than previously available. This allowed researchers to get a more complete picture that places the timing of barn swallow differentiation or speciation (i.e., when the barn swallow subspecies separated) closer to that of when humans began to build structures and settlements.

“The previous studies were playing with the idea of potential impact on population sizes due to humans”, said Chris Smith, a graduate student in EBIO and the Interdisciplinary Quantitative Biology program, and the study’s lead author. “Our results suggest a much more substantial link with humans.”

These new preliminary findings also suggest that this evolutionary link may have been forged through a “founder event”, which is when a small number of individuals in a species take over a new environment and are able to expand their new population there thanks to an availability of resources and an absence of competitors. For barn swallows, this event may have occurred rapidly when they moved into a new, relatively empty environment: alongside humans.

“Everyone is always wondering how do you study speciation? It’s been viewed as this long-term, million-year (process), but in barn swallows, we are not talking about differentiation within several thousands of years,” said Safran. “Things are really unfolding rather rapidly.”

Smith concurred: “It’s interesting to study speciation in the beginning steps.”

Egyptian sacred ibis mummies, Cuvier, Lamarck and evolution


This video says about itself:

Sarcophagus for the mummy of a sacred ibis. Egypt, Ptolemaic Period

3rd century BC – Polychrome wood – Height: 23 cm. Length: 44 cm. The piece is inscribed with a Demotic text.

From PLOS:

How Sacred Ibis mummies provided the first test of evolution

A charismatic personality set back the acceptance of evolution 50 years before Darwin

A debate over mummified birds brought to France after Napoleon’s conquest of Egypt played a central role in delaying acceptance of evolutionary theory; an episode in the history of biology revealed in an Essay published September 27 in the open-access journal PLOS Biology by Caitlin Curtis of the University of Queensland in Brisbane, as well as Craig Millar, David Lambert. The debate between the naturalists Georges Cuvier and Jean-Baptiste Lamarck took place five decades before Charles Darwin published The Origin of Species.

Cuvier had developed a theory of bodily form and function called the “correlation of parts“, in which every part was integral to the function of the whole. In this model, evolution would be disastrous, and thus Cuvier argued for “the fixity of species“, accepting extinction but not gradual adaptation to new environmental conditions. Lamarck, meanwhile, proposed a gradual transformation of species over time in response to environmental changes. While today Lamarck is most famous for incorrectly arguing for the “inheritance of acquired characteristics” as a mechanism of evolutionary change, Curtis, Millar, and Lambert note that he was an important theorist and champion of evolution fifty years before Darwin.

In 1798, Napoleon invaded Egypt, and scientists accompanying the army brought back to France hundreds of mummified animals, including many Sacred Ibises, revered by ancient Egyptians. Cuvier examined these birds, and correctly linked them to recently collected, unclassified birds in the collection of the National Museum of Natural History in Paris, making him the first scientist to test the idea of evolution. The similarity between the ancient and recent specimens indicated to Cuvier that the bird had not changed form in two thousand years, and thus supported his idea of the fixity of species. Lamarck disagreed, arguing that much more time would be needed to accumulate observable change in a species.

In 1802 the two scientists (and another colleague from the Museum) noted the similarity of a collection [of] Egyptian animal mummies to contemporary specimens, and presented this information to the French Academy of Sciences. Cuvier and Lamarck subsequently disagreed about the significance of these findings, however, and continued the argument for more than two decades. Curtis and colleagues argue that Cuvier’s greater public prominence and dramatic presentation style tipped the scales in favor of his incorrect theory, which was not effectively refuted until after Lamarck’s death in 1829, and continued to influence scientific opinion until the publication of Darwin’s theory reshaped evolutionary thought in 1852.

“The case of the Sacred Ibis highlights the disproportionate influence that a charismatic and dominant personality like Cuvier can have”, according to Curtis and her colleagues. “His unwillingness to consider the potential for the accumulation of small differences over long periods of time set back the acceptance of evolution for the next five decades.”

“In the late 18th/early 19th century, debates such as these often took place in public spaces like the halls of the Paris Museum.” Curtis said. “These days, public debates may have shifted to social media and news outlets, but debates about important scientific issues are still taking place and have a big influence on policy and society. The story of Cuvier highlights that although 200 years have passed we are still grappling with the issue of dominant personalities in science having disproportionate influence on its direction.”

Ancient Egyptians gathered birds from the wild for sacrifice and mummification. DNA study rejects the idea that Egyptians domesticated sacred ibis for ritual use: here.

Clown fish, why white stripes?


This video from Australia says about itself:

Never-Before-Seen Footage of Clownfish Hatching

5 January 2018

Thanks to the use of a specialized infrared camera, we’re now able to witness a never-before-seen phase of clownfish development: the nighttime hatching of larva from their eggs.

From the Series: David Attenborough’s Great Barrier Reef: Builders.

By the CNRS in France:

Clown fish: Whence the white stripes?

September 4, 2018

Summary: Scientists have been training their attention on the developmental and evolutionary determinants of white stripes in clown fish. They now detail why, when, and how these bands arose and help elucidate their role in clown fish social organization.

Coral reef fish are known for the wide range of colors and patterns they display, but the mechanisms governing the acquisition of these characteristics are still poorly understood. These researchers focused on clown fish, a group including thirty-some species distinguished by numbers of white stripes (zero to three) and by their colors, including yellow, orange, red, and black.

The team first demonstrated that stripes are essential for individual fish to recognize others of their species. Such recognition is critical to the social organization of clown fish living among sea anemones where several species may be simultaneously present and young fish seek to establish permanent homes.

The researchers then deciphered the sequences of stripe appearance and disappearance during the life of a clown fish. Stripes appear one at a time, starting near the head and progressing towards the tail, during the transition from the larval to the juvenile stage. The team further observed that some stripes are occasionally lost between the juvenile and adult stages, this time beginning at the tail end.

In an attempt to understand the origin of these patterns, the scientists delved into the evolutionary history of clown fish. They discovered that their common ancestor sported three stripes. Just like today’s clown fish, these ancestral stripes were made up of pigmented cells called iridophores containing reflective crystals. Over the course of evolutionary history, some species of clown fish gradually lost stripes, resulting in today’s range of color patterns.

The research team would like to follow up by identifying the genes that control the acquisition of white stripes for a greater understanding of how they evolved. This should clue them in to the processes behind color diversification and the role color plays in the social organization of reef fish.