For the past 50 years, scientists have asked the question “how did life begin?” Some start from the present, moving backwards in time to lifes’ simpler ancestors. Others start from the formation of Earth, 4.55 billion years ago, exploring how different chemicals might have organized to become living things. It’s a question science is still looking at, and however you look at it, it’s all fascinating!
Looking for the oldest fossils of a living thing, palaeontologists have found fossils of microbes dating back at least 3.4 billion years, with older rocks suggesting that organisms were able to use photosynthesis (convert carbon dioxide in to other elements, like sugars, by using sun light) up to 3.7 billion years ago!
Currently, all free-living life uses information carried in DNA as a kind of Construction Foreman – instructing cells to do certain things at particular times; experiments suggest that early life didn’t use DNA, but used RNA, which later evolved in to DNA as more complex life evolved. Scientists are now running experiments in which RNA-based cells may be able to reproduce and evolve.
Scientists have been able to create the building blocks needed for life to arise; They ran an electric current through a mix of ammonia, methane, and other gases believed at the time to have been present on early Earth. They found that they could produce amino acids and other important building blocks of life. Since the first of these experiments, science has takes in new information and with the latest experiments that were conducted with this in mind, the results were basically the same.
But just WHERE did these building blocks come together!? Based on the evidence we have, scientists think that they either came together in places such as:
- the scalding hot, mineral-rich waters streaming out of deep-sea hydrothermal vents, or
- Tidal pools or oceans covered by glaciers.
Amazingly, we’re coming to learn that objects like comets and meteorites may have delivered compounds from outer space! NASA and the European Space Agency have launched probes that will visit comets, narrowing down the possible ingredients that might have been showered on early Earth.