Evolution is the generally-accepted answer to how life arose, but how did non-living matter transition into living organisms? A team at the University of Wisconsin-Madison is trying to recreate the cradle of life, by gently rocking a combination of key minerals and organic molecules to see if certain chemical reactions give birth to life. If life emerges "easily" from these conditions, it could change our understanding of how common life might be across the universe.
Synthetic life has been created in a lab before. Back in 2010, scientists successfully created a brand-new bacteria by injecting a computer-designed genome into an existing cell, which was then able to replicate itself. A few years later, another team built artificial, self-assembling cell membranes, which could act like the "hardware" to house an artificial genome. More recently, researchers developed a semi-synthetic organism with extra genetic information in its DNA.
But if those scientists were essentially "playing God" by directly creating new life, the UW-Madison project is "playing Mother Nature" by trying to recreate the overall process of evolution itself.
The study of life's beginnings, or abiogenesis, has been ongoing for the better part of a century, and there are several theories for how non-living molecules first gave rise to living cells. Probably the best known is the idea of primordial soup, which suggests that when sources of energy, such as lightning or sunlight, interacted with Earth's early atmosphere, organic compounds would have formed and interacted with each other. These eventually gave rise to amino acids – the building blocks of life – and in turn, simple life forms.
But in the specific theory that the UW-Madison team is testing, those external energy sources aren't needed. Instead, organic compounds could have collected on the surface of iron pyrite (a mineral made of iron and sulfur), and these minerals could serve as the catalyst to kickstart early metabolism. That idea comes from the observation that iron-sulfur catalysts are still key to the function of modern cells, a possible time capsule for how that process got started.
The researchers mixed particles of iron pyrite and organic chemicals into vials, and attached them to a device that gently rocked them. The idea is that the chemicals will bind to the surface of the pyrite and, aided by the catalyst, begin replicating. Successful "populations" of the chemicals will then spread to other beads of the pyrite and continue to propagate.
The most effective and efficient colonies of the chemicals will spread across the most pyrite beads, and the team regularly moves some beads to new vials, allowing them to continue to expand. If it all sounds suspiciously like natural selection, that's kind of the point. Except here, the team calls it "neighborhood selection," since the process works on groups, instead of individuals which aren't easy to define in this situation.
"This community-level selection could have taken place before there were individuals with traits that were both heritable and variable," says Kalin Vetsigian, a researcher on the project. "If you have good communities, they will persist."
So far, the team has gone through over 30 generations of the chemicals, with each generation marked by a switch of the material to a new vial. They researchers are currently keeping an eye out for changes that might indicate lifelike chemical cycles have taken hold, such as the generation of heat, the consumption of energy or a change in the amount of material that sticks to the pyrite.
"The view that I've come around to is that lifelike chemistry may pop up relatively easily in many, many geological settings," says David Baum, lead researcher on the project. "The problem then changes. It's no longer a problem of 'will it happen,' but how will we know it happened?"
The study could have implications beyond how life arose here on Earth. If life arises relatively "easily" under certain chemical conditions, it might be more widespread on other planets.
"If we find many different chemistries supporting lifelike reactions, we can expect more origins of life elsewhere in the universe," says Baum.
A research paper outlining the process was published in the journal Origins of Life and Evolution of Biospheres.
Source: University of Wisconsin-Madison