Engels was a dialectical materialist. In no way did he minimise the importance of thought - rather he explained how it arose. We can also see that Benjamin Franklin, the eighteenth-century US politician and inventor, was much nearer a materialist approach than Hegel when he defined man as a “tool-making animal.”
Darwin showed a hundred years ago that there is a struggle for existence, and species survive through natural selection. At first sight early humans didn't have a lot going for them, compared with the speed of the cheetah, the strength of the lion, or the sheer intimidating bulk of the elephant. Yet humans came to dominate the planet and, more recently, to drive many of these more fearsome animals to the point of extinction.