What is the magic of an island? Surviving on the island in just 5,000 years, the mammoth lost weight from 6 tons to 2 tons

Before humans made their fortunes, mammoths, the behemoths covered in hair, were probably the most widely distributed mammals on the planet. They shuttled between the Eurasian continent and North America, which can be said to be the most important, Most Influential Mammal.

As you may have heard, these epochal species did not wait for the dawn, before the end of the last ice age, some 10,000 years ago, and they went extinct.

However, this is not the case, and while the global mammoth is heading towards extinction, a small group of the species has survived. They entered Wrangel Island, 200 kilometers away, from the Siberian coastline when the ice age came, and then got stuck on it as the ice age ended.

In the "post-mammoth" era, this group of mammoths trapped on Wrangel Island did not really become extinct until about 3,700 years ago. At this time, the Yin Shang Dynasty in China had just overthrown the Xia Dynasty, and the real history of recording history in writing began. era.

If humans entered Wrangel Island at this time, this group of interesting animals might be recorded, but humans did not have enough technology to enter the island until 3,000 years ago, when all mammoths were extinct.

However, to the surprise of modern paleontological researchers, the mammoths on Wrangel Island were far from the mammoths we are familiar with. They only grew to about 1.8 meters and weighed only about 2 tons. , while continental mammoths can grow to 3.2 meters and weigh more than 6 tons.

The mammoths stranded on the island appear to have taken only 5,000 years to slim down themselves into 'miniature mammoths'.

For biological evolution, 5,000 years is just a blink of an eye, so what is it that makes mammoths change so amazingly in such a short period of time?

Island Rules: Big animals get smaller, small animals get bigger!

You may have heard of Komodo dragons before, which can grow up to 3 meters and weigh over 130 kilograms, making them the largest lizards in the world.

You may also have heard of elephant birds, which can be over 3 meters tall, weigh up to 500 kilograms, and are almost twice the size of their continental cousins, which did not become extinct until 1,000 years ago.

What the two species have in common is that they both live on isolated islands, which seem to have made them bigger, the exact opposite of the island mammoth.

In 1964, a Ph.D. graduate named J. Bristol Foster first described the change in body size of island animals. Simply put, small animals become larger after being isolated on islands, which is now the case. It is called "island gigantism", and the isolation of larger animals that cause them to become smaller is sometimes called "island dwarfism."

He personally believes that this is the rule for animals to survive on islands, and he also gives why creatures evolve in this way.

He believes that in an island environment, small creatures will face fewer predators and competitors, giving them enough room to grow larger.

But large animals like elephants don't need to worry too much about predators or competitors—their main concern is lack of resources to sustain themselves.

So for these naturally large animals, the smaller habitat means they have to be smaller to survive.

This explanation seems plausible, but in fact the size of island creatures is much more complex than this.

Island animals that don't play cards according to the routine

In 1978, another young biologist named Ted Case discovered that some organisms did not evolve according to this rule.

He has personally studied a large iguana, the chickwalla, and, in order to gather more data, it has searched the islands of the Americas for sightings of the chickwalla.

According to the island rules we mentioned earlier, the chuckwalla should get bigger on the island, but Case found that the island doesn't make the chuckwalla bigger every time. Some islands got smaller.

In addition to this, Case found an interesting phenomenon in which he studied the island of Angel de la Guarda in chuckwalla.

Open UC browser to see more wonderful pictures

The half-meter-tall Minorca giant rabbit, source: NobuTamu

On the island, there are still two kinds of rattlesnakes - the red diamond rattlesnake and the spotted rattlesnake, which do not evolve according to the island rules.

On the mainland, the red diamond rattlesnake is twice the size of the spotted rattlesnake, but on Angel de la Guarda, the opposite is true, where the spotted rattlesnake is almost twice the size of the red diamond rattlesnake.

These two animals that share the same ecosystem, according to island rules, should both grow bigger at the same time, but the truth is that one gets bigger and the other gets smaller.

In later research, Case found that the spotted rattlesnake was more divergent from its mainland relatives than the red diamond, meaning that the spotted rattlesnake isolated and evolved on its own earlier on the island.

This allows the spotted rattlesnake to integrate into the island ecosystem faster. It makes itself bigger through island rules, while the red diamond rattlesnake landed later, and their living space has been occupied by another kind of rattlesnake, so they can only quickly become smaller. body size to adapt to new environments to find their niche.

Case redefined the island rule for his new discovery, arguing that the central factor driving changes in an organism's size is energy expenditure, with all changes stemming from an animal's energy needs and how much it can get at any given time. energy.

In terms of energy consumption, each animal size has its own distinct advantages and disadvantages. When it comes to competing for resources, larger animals are better at storing energy for emergencies.

But small animals need fewer resources to begin with, and at the same time they are more capable of reproducing, which means small animals are better able to cope with environmental crises and survive dramatic changes.

In short, whether the animals on the island got bigger or smaller had less to do with their original size and more to do with what kind of support the existing ecosystem on the island was able to offer.

The fact that the energy demand causes dramatic changes in animals doesn't just happen on islands, it happens anywhere, it's just islands that magnify the results because there's a single determinant of how much energy an organism can get.

In addition, energy requirements are not only affected by body size, but other characteristics are also affected by this, just because body size changes more easily, which is why the mammoth lost 4 tons in just 5,000 years.

at last

So far, there has been a lot of controversy about whether it's "island gigantism" or the so-called island rule, but personally, I still believe that it's energy that controls it all, after all, the activities of living things are driven by energy.

I don’t know if you have ever thought about where is the largest isolated island on earth? How would creatures evolve on such an isolated island?

In fact, there is a perfect giant island on the earth, that is, the South Pole, and the ocean around it.

There is an ocean current that surrounds the entire continent from west to east in the Antarctic waters. This is the strongest ocean current on earth and is the main reason why Antarctica is so cold. It isolates external resources from entering the Antarctic waters.

At the same time, deep-sea animals tend to develop larger sizes, which is called "deep-sea gigantism", so some people believe that there may be giant animals that are undiscovered and beyond imagination in the world in the Antarctic waters.