Since Miller first simulated the birth of life in a laboratory, the problem
has been to account for the fact that those elements could be produced in
one location rather than spread in an ocean. The chances of the right elements
getting together in the same place at the same time is minuscule.
Wills and Bada show how a beach could have provided the "filtering" process
needed to get the aminoacids together. Tides washing ashore provide a
natural filter because a beach is layers of chemicals that react differently
with whatever is washed ashore. In particular, organic elements would tend to
pile up in the same layer.
Wills and Bada also analyze the findings from the Murchison meteorite that fell in 1969 in Australia (it includes organic matter than is very similar to Miller's elements).