Compared to terrestrial creatures, the animals of the island have always been known for their exceptional size. From dwarf elephants, mini chameleons, ‘hobbits’, to giant mice, why is that?
In the past, people have discovered that isolated islands look like a place of curse. Most of the “inhabitants” who had migrated from the mainland to the island were unable to escape, and their body shape began to change significantly compared to their land brethren.
This is also known as the “island law”, which is an ecological geographic law in evolutionary biology. In general, among animals that migrate from land to island, large animals tend to be smaller, and small animals tend to get bigger – this is called giantism. Island gigantism. For example, an extinct species of giant hutias in the Western Indian Ocean Islands is the largest known rodent. Its weight can reach a staggering level (about 200 kg), equivalent to that of an American black bear. Another famous example is the Dodo bird on the island of Mauritius. Due to the fact that the island’s environment is devoid of predators, they have also grown to form large and flightless. In contrast to island giantism, a condition where body size becomes smaller after immigration to an island is called Insular dwarfism. The most typical example is the dwarf elephant found many times on islands around the world. Elephants have always been known to be the largest terrestrial stump, but some dwarf elephants can only reach the size of a pig. Those who have read Odyssey will be impressed by Cyclops. According to speculation, the Cyclops prototype was a dwarf elephant. 2000 years ago, the Greeks probably excavated the remains of a dwarf elephant on an island near the Mediterranean Sea. Its skull size was almost twice that of a human skull. Perhaps it was because they had never seen an elephant, so the Greeks imagined it as the skull of a one-eyed giant, and related rumors and myths were born from this. Animal species that also dwarfed the island environment also included species such as dwarf mammoths, small hippos and Florida island deer, all of which were one size smaller than their terrestrial counterpart. Among them, the most extreme dwarf island fauna is the mini chameleon (Brookesia micra) of Hara Island in northeastern Madagascar, Africa. It is the smallest chameleon known to mankind, the largest one measuring no more than 3 cm. It is worth noting that this dwarfism does not only occur in ordinary animals. Even we humans cannot escape the law of the island. The pop culture dwarves are not unfounded, the “hobbits” are real. Flores island in Indonesia has an area of only 14,000 square kilometers, but on this small island there used to be a small group of people who used to live. They are also “cursed” by dwarfism and this affects their stature. According to estimates from nine known fossils, this ancient human was only 1 to 1.2 meters tall and weighed about 25 kg. As we all know, the average 6-year-old modern person’s average height is more than 1.1 meters tall. This inevitably reminds people of the hobbits in “The Lord of the Rings”, so the ancient people on Flores were also known as “hobbits”. From a taxonomic point of view, the Flores belong to the same genus as us. Hence, they are also the smallest known human species. The ancestor of the Flores was Homo erectus. About 200,000 years ago or earlier, they moved on to Flores Island. Compared to the mainland, the island’s resources were very limited and the Homo erectus people were often hungry due to lack of food. If the people are short, there is a better chance of survival because they need to eat less. As a result, the dwarf gene is passed from generation to generation, and eventually develops into Floresians. Biological evolution has shown more than once that some strange things will happen on the islands. And from the changes in body shape of the other animals on Flores Island, you can feel the power of the law of the island. At that time, on the island there was a species of elephant named Stegodon florensis, only 1.5m high and weighing no more than 800kg. Their land-based compatriot is the elephant Stegodon zdanskyi. They are stronger and more powerful than modern African elephants, this species is about 3.8 meters tall and weighs 12 tons. But not all of the animals on this island have been reduced to the same size as the Flores and the Stegodon florensis, in fact, the small terrestrial animals that migrate here will achieve a Giant size beyond imagination. The most typical example is the Flores Giant Rat, since without natural predators, they are not even afraid of humans. Of course, this giant rat does not threaten the survival of the Flores Island biological population. Except for some insects, the giant rat Flores is mostly vegetarian. It can be said that biological evolution on the islands took place in a very strange way. Therefore, scientists always think of the first word “island” when discovering creatures with anomalous body shape. So what is the factor that causes the animals on the island to change their body shape? For many years, scientists have always wanted to summarize the general nature of the rules on the island, and try to solve that mystery. The first person to try to explain this phenomenon was a biologist named J. Bristol Foster. Therefore, this ecological geophysical law is also known as “Ford’s Law”. In 1964, his dissertation compared 116 island species with terrestrial species and plotted them in a table. In an article titled “Mammal Evolution on Islands,” Foster said that among the new “inhabitants” of the island, rodents tend to grow larger. Predators and ungulates will tend to be dwarfed. In general, large terrestrial species will be smaller and smaller land species larger on islands. In this regard, Foster also provided some tentative explanations. The number of species on the islands is much less than on the mainland, and the number of predators and competitors will decrease accordingly. This seems to be an advantage for small rodents. Because they do not have a predator, they always have a sufficient source of food and can control their fertility rate well. But hippos, deer and other large animals cannot do this. A lack of predators would also mean an overabundance and a shortage of food. Consequently, the smaller members of the population will have a higher survival rate and begin to affect the entire population. They grow from generation to generation and their sizes are getting smaller and smaller. Foster’s paper is simple, but at the time it aroused strong interest in the scientific community. Thereafter, more extensive research was conducted on the island’s organisms, and the island law was a little more refined. In fact, large organisms have more food choices and more easily control other species. Small organisms, on the other hand, require fewer resources, shorter reproductive cycles, and adapt faster. Therefore, in the island ecological environment, where every aspect is limited, these factors are very important and have special effects. Subsequent studies also found that the speed at which the island’s animals change body shape was indeed staggering. 24 km from the French coast, there is an island named Jersey. About 6000 years ago, the deer came here and completely isolated from the mainland. As a result, in this short time of thousands of years, the red deer on the island has shrunk by 1/6 of that of the people on the mainland. Fossil records show that it only took 5,000 years to dwarf a population of elephants from 4 meters in height to about 1 meter. However, it should be noted that the island laws are only a general model of evolution, not absolute law. The environment on an island includes many different factors, such as the size of the island, climate, natural history, habitat, biological relationships, etc.These factors will also affect the size of the island. animals on the island to a certain extent.
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