The cost of intelligence
Intelligence is one of these fuzzy concepts that are so difficult to define formally. We all have some intuitive idea of what it is to be intelligent and in most cases involves some capability to solve new problems and learn from past experiences. So, it is intelligence something unavoidable in evolutionary terms? and, as the article asks:
It is important to make clear that most "complex" species have some degree of intelligence and that even fruit flies are capable of learning. According to the article, most species with a nervous system (and some without them, just using their genetic network, and network is here the keyword) can behave non instinctively.
What is more interesting, it is possible to obtain smarter flies by selecting, in a lab, for those individuals that are more capable of learning. In only 15 generations the researchers found that the flies have evolved to learn faster. So why don’t you see smarter flies in the wild? When you mix these "smarter" flies with the original kind they found that the smarter kind where less likely to survive. Actually when the "smart" flies were places in a nutrient-poor environment and allowed to evolve the researchers found that after 30 generations the flies were less clever. It seems that brains come with a price tag and it might be that only very specific environments lead to a selective pressure that could make a complex neural system such as ours (that consumes 20% of all calories burned at rest) something worth investing in. It should be also an environment in which non specialised agents can buy enough time to learn and improve.