Professor Mike, this is a caricature of Marxism. There is no such doctrine of "inevitability". Perhaps you have not read Marx, but commentary on Marxism instead. I myself made this mistake 4 decades ago when I was an undergraduate.
I recommend Paul Sweezy's consideration of the Communist Manifesto which appeared in a recent Monthly Review for a much more accurate understanding of the marxist view of "inevitability." Sweezy takes note of a paragraph in the CM that reads:
"The history of all hitherto existing society is the history of class struggles. Freeman and slave, patrician and plebeian, lord and serf, guild-master and journeyman, in a word, oppressor and oppressed, stood in constant opposition to one another, carried on an uninterrupted, now hidden, now open fight, that each time ended, either in a revolutionary reconstitution of society at large, or in the common ruin of the contending classes."
What could Marx be referring to when he speaks of the "common ruin of the contending classes?" In Sweezy's view, this eventuality could be the ecological ruin of the world if capitalism is not overthrown. Such a catastrophic ending--with the looming threat of global warming, species extinction, etc.--would not only make life unlivable for the workers, but the rulers as well. His proposal is that the Marxist movement orient toward the scientific community in order to join forces against this danger. This sage's call for a red-green synthesis should be heeded by all of us who are committed to Marxism:
"Already, a very large section of the world’s scientific community is fully aware of the seriousness of the ecological threat facing the planet, but what is not widely recognized is that the cause of the threat is capitalism itself. Bourgeois economics seeks to hide or deny this fact. No wonder. If it were generally understood, capitalism would soon be identified for what it is, the mortal enemy of human kind and many other forms of life on the planet. In these circumstances, our responsibility is not only to help the ecologists to get their message across, important as it is, but to convince the ecologists themselves as well as the public at large of the truth about capitalism, that it must be replaced by a social system that puts the life giving capacity of the earth as its first and highest priority. As the unfolding of capitalism's deadly consequences proceeds, more and more people, including 'bourgeois ideologists who have raised themselves to the level of understanding the historical movement as a whole,' will come to see what has to be done if our species is to have any future at all. Our job is to help bring this about in the shortest possible time."
Louis Proyect
(http://www.panix.com/~lnp3/marxism.html)