In the animal kingdom, humans are the only species that feels the need to support their progeny into adulthood. Exactly half of baby boomers (50%) have been the primary support for their children, be they under or over 18, in the past year. Another 17% gave some financial assistance to children over 18.
Of these same boomers, 20% also helped their parents financially. Score one for humans!
Source: Pew Research Center survey of 1,117 boomers, ages 41 to 59, http://pewresearch.org , 2006.