2024-01-12 19:56:07
Come the animals They come in all shapes and sizes, and many have distinctive features that make them unforgettable. From giraffe’s long necks to elephant’s distinctive tusks, here’s how 5 fascinating animals evolved their distinctive traits over the ages
Turtle shells
For years, scientists have debated how turtle shells evolved. According to a report published in the journal Current Biology, paleontologists once believed that the shell was formed by the fusion of osteoderms — bony deposits that make up the protective scales of crocodiles and armadillos.
But evolutionary biologists disagreed with this theory, given how modern turtle embryos developed. Instead, they believed that the ribs under the bodies of turtle ancestors gradually fused and united above the body to form the shell.
Giraffes’ long necks
Giraffes’ necks can reach 10 feet (3 metres) in length, allowing the animals to reach the foliage of tall trees. But they didn’t always have this great advantage.
Discokeryx xiezhi is a sheep-sized animal, an ancient relative of modern giraffes that lived about 17 million years ago during the early Miocene epoch (23 million to 5.3 million years ago). It had a short neck and a thick, disc-shaped skull.
Scientists proposed in 2022 that the thick skulls of D. xiezhi evolved to withstand powerful blows to the head during fights between males. Those same spells fueled the growth of their necks to aid in combat. This is called the “necks for sex” hypothesis, and suggests that competition led to the growth of longer necks. Males who won fights more often passed these genes on to their offspring than losers, eventually leading to the giraffes we see today.
Elephant tusks
Elephants have deep-rooted tusks that protrude from their mouths and grow continuously. These tusks are actually huge teeth that give the chicks an evolutionary advantage when digging, lifting objects, stripping tree bark, and protecting themselves.
The oldest known tusks were found in Dicynodonts, a group of stocky, pig-like herbivores that lived 270 million years ago, and had unique pointed beaks with protruding teeth on either side.
The size of giant blue whales
Blue whales (Balaenoptera musculus) are the largest animals that have ever lived. Their size makes it hard to believe that giant marine mammals evolved from a dog-sized ancestor, Pachycetus. According to a 2016 study in the journal Biology Letters, the size of baleen whales, including the blue whale, has increased significantly over the past 5.3 million years.
One of the main reasons for this accelerated growth is the filter-feeding behavior of baleen whales, which use bristle-like teeth to sift plankton from the ocean. This somewhat “passive” feeding strategy is related to the highly efficient metabolism that allows whales to conserve large amounts of energy while traveling long distances.
Researchers believe that the massive growth of baleen whales began in the Pleistocene era (2.6 million to 11,700 years ago). Heavy runoff from the ice seeped into the ocean, creating dense patches of plankton and krill. The high productivity of the oceans, combined with whales’ reduced use of energy, led to a huge growth spurt in the animals, allowing them to reach the enormous sizes we see today.
Tiger stripes
Tiger stripes vary between individuals, like fingerprints on humans. Markings play an important role in helping the tiger stay hidden while hunting prey. The stripes help break up the animal’s body shape, allowing it to blend into the tall grass.
In 1952, British mathematician Alan Turing theorized that a chemical reaction between two homogeneous substances was responsible for the famous tiger stripe pattern, along with other patterns common in nature. He called these substances “morphogens.” One acted as an “activator” and the other as an “inhibitor” – where the “activator” caused a band to form and the “inhibitor” created an empty space.
In 2012, a study in the journal Nature Genetics experimentally validated this theory by identifying genes that play a role in the formation of ridge patterns in the mouths of mice.
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