The Western Roman Empire collapsed when barbarian king Odoacer deposed of the infant Romulus Augustulus on September 4, 476. Germanic invasions had been causing economic and political problems for the Western Empire for decades, but the last emperor's fall is often used to mark the end of the Western Roman Empire.
When we talk about omnivorous animals, such as humans or pigs, we mean animals that eat all kinds of organic substances. The big difference is that in the case of the pig the prefix omni – (everything) refers to “everything” literally:plants, worms, insects, tree bark, dead animals, garbage, excreme