100 - Do playfights train meerkats for the real fights, or are they just fun?

200 - What was the youngest recorded age for allolactation?

300 - There is no such thing as a truly altruistic act said this 18th century philosopher.

400 - But in standing sentinel duty, offering food to begging pups, teaching young and other altruistic acts, non-parental meerkats seem to have disproved his belief. In truth, it seems to be that meerkats and other altruistic species are benefiting in some way from their "altruism". By helping to rear enough of one's relatives, an animal can help pass on as many (or more than) these as from rearing their own young. What is is they are hoping to pass on?

500 - In a study published in Science in Oct. 2003, it was shown that within 15 bird and 3 mammal species tested, altruistic helpers are better at distinguishing close from distant relatives and non-relatives in those species where they get the most benefit from helping relatives pass on their genes (i.e. you must make discriminations much better when you have more to gain).  Name one of the bird and one of the mammal species studied.