Table 1.

Evolutionary and anthropological events that ultimately gave rise to the emergence and proliferation of influenza type A strains within humans.

Event	Time (approximate)	Origin	Reference
Evolutionary emergence of first RNA viruses	3.5 billion years ago	Primeval biosphere	[6]
Evolutionary emergence of first wild ducks	65 million years ago	Archaic waterfowl	[7]
Evolutionary emergence of first influenza A virus	Unknown	Presumably wild duck intestine	[8]
Evolutionary emergence of first hominids	3.6 million years ago	Africa	[9]
Domestication of wild boar	8000 BC	China	[10]
Domestication of red junglefowl	8000 BC	Vietnam	[11]
Introduction of domestic junglefowl (chicken)	6000 BC	China	[11]
Domestication of wild duck (mallard)	5000 BC	China	[12]
Rise of first pandemic influenza strains	4000 BC	China (conceivably)	[13]
Domestication of wild horse	3500 BC	Kazakhstan	[14]
Domestication of wild turkey	1000 BC	Mexico	[15]
Domestication of wild quail	1100	China	[16]
Introduction of pigs into America	1539	Mexico Gulf coast	[17]