|Fig 1 from McInerney and O'Connell News and Views|
outlining suggested evolution of Eukaryotes.
As Denis Noble points out in his wonderful book Dance to the Tune of Life the fact that the Eukarya evolved from symbiosis two different domains is a striking instance of how the simplistic "selfish gene" stuff gives a highly misleading picture. Life is in fact an exquisite balance of cooperation and competition, and that fact that all animals, plants and fungi are based on this symbiotic fusion is truly remarkable.
When the Archaea were discovered it was believed that the "family tree" looked like Fig 2. It's truly amazing how much has been discovered since I was an undergraduate, and how much more there must be to find!
|Fig 2: From Woese 2000 Interpreting the universal phylogenetic tree|