#evolutionary adaptation

[covenawhite66]

Soon After Dinosaur Decimation, Our Primate Ancestors Began Pouncing on Prey

Nails helped them climb trees quietly, and forward-facing eyes helped with depth perception to aid in precise leaping

Small primates like Teilhardina, which lived in the forest canopy of ancient China 55 million years ago, were early adopters of some of our evolutionary family’s most famous characteristics.

Our gifts of depth perception, dexterous hands and more can be drawn back to a time much closer to the dinosaurian heyday than the present. The first primate with a grasping toe dates back to 56 million years ago, the first big increase in brain size occurred 55 million years ago and the number of teeth we have can be traced back to 30 million years ago, Silcox points out. But exactly why our early ancestors came to have such telltale traits has been debated by experts for decades.

Nails would be quieter than claws while sneaking up on prey, for example, and the ability to leap would allow early primates to get the jump on their prey, with binocular vision being critical for gauging the distance. To test this idea, Wu and colleagues didn’t look to fossils—they looked to genes involved in what primates digest and how those genetic markers have changed over time

[smallinsaneone-blog]

Today in physical anthropology we learned that evolutionarily, women prefer men with broader shoulders and narrower hips. So basically we're evolutionarily adapted to be attracted to Chris Evans.

[bberwyn]

Can snowshoe hares survive global warming? Photo courtesy Kim Fenske. ‘That mismatch does indeed kill’ Staff Report For millennia, snowshoe hares have camouflaged themselves from predators by blending in with their surroundings, turning pure white in the winter to blend in with the snow, then brown in the summer. But climate change is shifting the timing of the snow season, and the hares may not…

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[phacopida]

Evolution in Shorebirds

These Godwits (Black-tailed above, Bar-tailed below) have the tell-tale shorebird (or wader) traits of long legs and beaks well adapted to feeding on the shoreline. Generally grouped in Aves Order Charadriiformes, modern genome sequencing is failing to show the order contains a last common ancestor (i.e., the group is paraphyletic). I find this not surprising. Given shorebird success and diversity, why would you not observe convergent evolution of beaks and legs, that is, the same features separately evolving in species that have different lineages.

The beautiful 19th century art work at the top well illustrates another phenotypical shorebird trait, sexual dimorphism, a powerful natural selection mechanism for evolution of species.

The lower illustration by the same artist is of the Godwit species Limosa lapponica, a shorebird noted for the longest known non-stop flight of any bird, some 6000 miles in 9 days; from dinosaur to longest flight, how’s that for an evolutionary biology anecdote.

Classification for both: Aves Order Charadriiformes, Family Scolopacidae, Genus Limosa

Also see post about shorebird (Charadriiformes) beak variation

Image from: The Birds of Europe, 1st Ed. (1832-1837) by Elizabeth Gould & Edward Lear, Circa 1830.

[paleoteacher-blog]

Walliserops trifurcatus Trilobite Evolutionary Enigma

Class Trilobita, Trilobites Order Phacopida, Family Acastidae Geologic Time: Devonian Fossil Site: Zagora, Morocco

"The trident is unprecedented among more than 20,000 trilobite species, an evolutionary enigma, and a functional mystery. Many hypotheses have been put forth regarding why the adaptation took place and the purpose. The appearance of such a prominent phenotypic trait would ostensibly require considerable “evolutionary energy”, for which some substantial selective advantage would be expected for its possessors. Energy would also be expended to grow, and possibly regrow, the protuberance which might have made shedding its exoskeleton more difficult, and it hardly benefitted the trilobites steamlining. Moreover, the trident itself lacks the bilateral symmetry, curving away from the body axis, and distinctive trait among most animals, arthropods and trilobites. Further, there is variability in the trident curvature, with shorter tridents more curved. Several uses of the trident have been discussed: 1) a means of levitating above the seafloor; 2) sophisticated sensory organ; 3) a mechanism for hiding or defending; 4) a mere adornment of sexually (dimorphic) selection as in the staghorn beetle; 5) sexual or caste polymorphism as in social insects. Of course, a combination is plausible, for example, sexually selected armament."

[eclecticirony]

Skydiving spiders? Talk about evolutionary adaptation.

Some spiders that live high up in the forest canopy could fall and die. But amazingly, some have evolved the ability to skydive, helped by their flattened morphology. The image above is of the genus Selenops in the Family Selenopidae, large spiders often called wall crab spiders, or more simply, called flatties. Read more here about their “directed aerial decent” and see a video.

Subphylum Chelicerata (Chelicerates), Class Arachnida (Arachnids), Order Araneae (Spiders), Infraorder Araneomorphae (True Spiders), Family Selenopidae (Flatties), Genus Selenops

[nashs-mango]

The chicks of the Amazonian bird Cinereous mourner (Laniocera hypopyrra) mimic toxic caterpillars of the flannel moths both in appearance and behavior.

[eclecticirony]