Picture an alien. Is it a grey figure with huge eyes, a green tentacled creature with a giant brain or a terrifying scaly monster with sharp teeth and claws?

If we ever have an alien encounter, we might find that they resemble us a lot more than we expect. A research project has found that humans might be part alien.

Humans are made up of a complex composition of chemicals. There are 21 elementsSimple substances making up everything, substances that cannot be broken down into smaller parts. in our bodies, which together form dozens of different substances.¹

One group of chemicals is peptides. When joined together peptides form proteinsA kind of molecule that drives all biological processes. They make up around one-fifth of our total body mass and without them our bodies could not function. They fold into 3D shapes, making them extraordinarily complicated as a whole.: the substances that help our body stay alive. They have a huge array of functions, from fighting illness to digesting energy from food, to helping us to sleep.

The new research finds that interstellar medium - the matter that makes up space between the stars - provides the perfect conditions for peptide creation.² 

The peptides that make life possible might have formed in space then arrived on Earth in a meteor or comet.

Perhaps this makes us aliens, native to the stars rather than the Earth? Indeed, the particles that allow us to exist could predate the formation of the planet itself.³ Early lifeforms may have even arrived on Earth already living.

Besides, we arguably act like aliens towards our own planet. We exploit, reshape and damage it. Like the Martians in HG Wells' classic novel War of the Worlds (1898), we have wreaked untold damage on the Earth and used its resources for our own ends.⁴

Others find this idea absurd. There is no firm evidence that we actually came from space particles. Our research can only take us back so far.

But even if the matter that makes us comes from space, we are creatures of this planet. We are the result of a chain of evolution that takes place in Earth's unique conditions. We cannot live in any other known atmosphere. If we are not native to Earth, then nothing is.

Are we all aliens?

Yes: We were born in space and to space we will return. We have spacecraft. We often subjugateForcefully bring under control. other living things.

No: We might be made of cosmic particles, but we exist thanks to the combination of resources - air, water, sunlight, soil - that only the Earth provides.

Or... It is a matter of perspective on what is more important: raw materials or the process that ties them together. Besides, if all life derives from space dust, then all planetary life is somehow alien.

Elements - Simple substances making up everything, substances that cannot be broken down into smaller parts.

Proteins - A kind of molecule that drives all biological processes. They make up around one-fifth of our total body mass and without them our bodies could not function. They fold into 3D shapes, making them extraordinarily complicated as a whole.

Subjugate - Forcefully bring under control.