Living things are hugely complex, However, all this complexity did not emerge fully-formed from ancient Earth. Instead life almost certainly originated in a series of small steps, each building upon the complexity that evolved previously. Experiments suggest that organic molecules could have been synthesized in the atmosphere of early Earth. Macromolecules arose from the chemical reactions among monomers. All living things must reproduce, copying their genetic material and passing it onto their offspring. This ability to copy the molecules that encode genetic information is a key step in the origin of lifeMost scientists propose that DNA (Molecule 2) developed from small changes to which of these molecules? A ATP B glucose CRNA D polypeptides
