My Year of Darwin 4/9/2014: Another piece of the origin puzzle

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"We do not steadily bear in mind how profoundly ignorant we are of the conditions of existence of every animal; nor do we always remember that some check is constantly preventing the too rapid increase of every organised being left in a state of nature. The supply of food, on an average, remains constant, yet the tendency in every animal to increase by propagation is geometrical" Charles Darwin, Voyage of the Beagle

Decades before the Origin of Species, we have 

1. Contemporary organisms are linked, genealogically, to their ancestors 

2. Extinctions are common if not the fate of most organisms

3. More organisms are born than can possibly survive

A few pieces are missing: traits vary,traits are passed from one generation to the next, some traits infer greater probabilities of survival and reproduction (fitness). Almost there Darwin!