• Question: How did life begin?

    Asked by DNCBrian to Alex, Ana, Clay, Keegan, Mark on 3 May 2016.
    • Photo: Mark Ritchie

      Mark Ritchie answered on 3 May 2016:

      Whether you believe in a Creator or not, the basic steps are probably the same. Without getting too detailed, an abundance of nitrogen, carbon and phosphorus allowed millions of different possible organic (carbon-containing) compounds to form in seawater. Some of these compounds, which resembled what we know today as nucleotides or the building blocks of DNA, liked each other and began to link together to form chains that then attracted other nucleotides that liked each other, leading to self-replicating molecules that specify the sequence of amino acid, what we now think of as DNA . In the past, all this was supposed to have occurred by chance, and many scientists thought it to be too unlikely. But very recently, a physicist named Jeremy England has shown that DNA formation and replication may be much more likely form than many other possible molecules, suggesting that life may be inevitable. As the forms of DNA changed over time and lengthened, different forms of life emerged, and through natural selection of more successful forms, we observe the evolutionary history of the earth.

    • Photo: Alexander Taylor

      Alexander Taylor answered on 3 May 2016:

      The short answer is that we don’t know.

      For life to evolve into all the forms we see today, it must have started with a molecule that could self-replicate, probably a “nucleic acid” like DNA or RNA. These associated with other molecules like “amino acids” (the building blocks of protein) and formed into larger and more complicated forms that eventually became cellular life as we know it. This seems very unlikely, but under the right conditions (what was once called “the primordial soup”) you could see self-assembly of DNA and amino acids.

    • Photo: Clay Robinson

      Clay Robinson answered on 3 May 2016:

      This is a difficult question, and the answer is, no one really knows for certain.
      There are two main reasons.
      1. No one was around to observe it happen.
      2. We cannot discover the answer using the scientific method, though people have tried.
      The most we have been able to do is make observations and try to work backward from those observations to guess what conditions might have been present and the circumstances necessary for life to begin. In many cases, though, all we have are hypotheses. We do not even have enough evidence to elevate those to the status of theories.
      But humans are curious, and we will keep looking for an answer.