We have long looked to the stars for signs of extra-terrestrial life, but aliens may have been living under our noses this whole time. Tardigrades are microorganisms that can survive in incredibly hostile environments, including the vacuum of space, and scientists are beginning to wonder if they evolved in an extra-terrestrial environment.
Wikipedia extract on tardigrades:
Tardigrades are water-dwelling, eight-legged, segmented micro-animals. They have been found everywhere: from mountain tops to the deep sea and mud volcanoes; from tropical rain forests to the Antarctic. Tardigrades are among the most resilient known animals, with individual species able to survive extreme conditions that would be rapidly fatal to nearly all other known life forms, such as exposure to extreme temperatures, extreme pressures, air deprivation, radiation, dehydration, and starvation.
Some of the characteristics that tardigrades possess make no sense in terms of Darwinian natural selection. The tardigrade can survive at temperatures of -272oC, whereas the lowest temperature ever recorded on Earth is -98oC. Another example of their unnecessary resiliency is the fact that they can withstand radiation levels up to 5000 times stronger than other animals on Earth can, and they do so via their own unique protein. It is not normal for an organism to exhibit traits that offer protection against problems that don’t exist, and tardigrades seem to have an abundance of unnecessary resiliency.
Bacteria developed resistance to antibiotics because it allowed them to circumvent a major threat to their survival; giraffes developed long necks because it allowed them to reach high-hanging leaves; polar bears developed white fur because it offered them camouflage while hunting prey. All of these adaptations made the survival and proliferation of each respective species more likely. Tardigrades are an evolutionary anomaly.
The unnecessary resiliency of tardigrades begs a thrilling question: what if tardigrades evolved in space, aboard a comet? This would explain their ability to survive in extreme environments: resistance to high levels of radiation would be an incredibly useful characteristic in the vacuum of space, where you don’t have the luxury of atmospheric radiation shielding. Other tardigrade characteristics, such as their ability to withstand extreme temperatures, would also be useful during interstellar travel. On their journey to Earth, tardigrades may have passed close to incredibly hot objects such as stars, and would have had to survive in the freezing conditions of empty space, which can be as low as -270oC.
The earliest fossils of tardigrades date back to around 530 million years ago, which just happens to coincide with the Cambrian explosion (a mass diversification event where most animal species appeared on the fossil record). A recent study suggests that the Cambrian explosion was facilitated by extra-terrestrial microorganisms that travelled to Earth on a giant comet, and it is plausible that tardigrades were aboard this comet or another similar one.
The proposal that tardigrades are an extra-terrestrial species goes against the widely accepted scientific viewpoint that tardigrades originated on Earth. This is supported by evidence that they share genes with other organisms and the fact that they seem to fit into the evolutionary tree (although their exact position in it remains uncertain). If tardigrades truly were extra-terrestrial in origin, their entire DNA framework would most likely be different to other organisms on Earth. The only way to explain away this discrepancy is to assume that an ancestor to all life initially emerged on some location outside of Earth; and seeds of life have been spread throughout the cosmos from this single ancestral source. All life would share the same DNA framework, so when the tardigrades came to Earth, their DNA was compatible with the organisms currently residing on the Earth, that also arrived on comets. This hypothesis may seem far-fetched, but it is backed by several reputable scientists, who believe that a paradigm shift on our understanding of the origin of life is imminent, and that comets regularly seed life on planets, creating an interconnected galactic biosphere.
There might be millions of aliens in your immediate vicinity, in the form of an awesome little creature: the tardigrade.