Is anthropology a science?

It is a social science, since much is based on conjecture and assumption based on available evidence. To be termed scientific, a method of inquiry is commonly based on empirical or measurable evidence. Anthropology does not fall into this category.

Physical anthropology is much more science based. It can be as much of a science as biology. There are certainly some that could legitimately call themselves scientists. Some of the other branches tend to rely more on conjecture.

Yes, it is. It's one of the most demanding, in fact.