Evolution is no longer the predominant force in shaping the human character. Changes due to natural and sexual selection occur for humans on a temporal scale too large to be seen in one lifetime. I recall hearing statements to the effect that in the far future, humans will have: larger heads to house larger and more powerful brains, frail bodies, and a lack of bodily hair. These projections were made on evolutionary trends over the last few millennia, and of course, are completely preposterous.
Evolution is not directional, Darwin has compared it with a bush that grows in every direction. Some of the branches are successful, some get pruned. This implies that our high level of intelligence and upright posture exist because they provided better solutions to problems in our ancestral environment. The structure and likeness of our bodies stem from a sequence of modifications, each adaptations to environmental changes across the millennia.
Humans are very well adapted (not perfectly, e.g. the cells on our retina face the wrong way, etc.) to a hunting and gathering lifestyle on the African savanna and possibly parts of Europe. Living organisms are elaborately adapted to their particular ways of life in the environments in which they evolved, there is no evidence for any other kind of adaptation. A stable species may be "perfectly" adapted to its environment, but there is not guarantee that the environment will be stable. Even without such ecological cataclysms as asteroid impacts, volcanoes, pervasive flooding or the encroachment of suburbia, the slow process of continental drift would eventually transform the environment sufficiently to necessitate phenotypic change.
A century of research in biology confirms Thomas Huxley's thesis: the universe is hostile to life in general and human life in particular, the evolutionary process and its products are contrary to human ethical standards; human survival and ethical advance can be achieved only in opposition to the cosmic process (Williams, 1993). Evolved psychological mechanisms solved the problems of the historical past, but they are not guaranteed to solve the problems of today.
Cultural change, on the other hand, is Lamarkian. Humans have changed their physical and social environment immensely over the past few millennia, especially in the last two hundred years. Reliable birth control technologies have short-circuited the relationship between sex and reproduction. Revolutions in agriculture and medical technology have significantly improved an individuals chances and length of survival. Our destructive capacity has also increased, we have nearly destroyed our civilization at least twice this century.
Changes in the human phenotype are likely to be largely superficial. The current medical ethic of many western nations appears to be: try to keep everyone alive as long as possible, regardless of the quality of that life or chance of long term survival. While this high value for human life was certainly adaptive for our survival in the ancestral environment, it may be contributing to the inefficiencies of our health care system. Of course, the healthy diet and proper exercise more likely to be obtained in our ancestral environment would be a great health benefit as well.
When everyone has a high chance of survival, those who have the most offspring will be successful. Due to reductions in infant and child mortality and increases in available resources, the average potential family size is larger than ever before. This large family size is kept in check by the use of family planning techniques. The cultural definition of "success" is no longer tied to the number of successfully reproducing offspring, but to the accumulation of material wealth far beyond that necessary for survival or reproduction.
An interesting phenomena is that those with high-status and high material wealth may actually have less children than those who are not so fortunate. Demographic trends predict that ethnic whites will decrease in proportion to non-whites over the next fifty years. These fluctuations in population size and proportions due to differential reproductive strategies may be "growing pains" of our rapid technological advancement. Many humans have not yet realized that overpopulation is not an evolutionarily stable strategy.
While concerns of overpopulation in developing nations are valid, at the same time industrial nations are guilty of plundering the earth's resources. I recall an article in a publication opposed to legalized abortion claiming that the entire population of the earth could fit into the state of Texas. While this may be physically possible, the author did not consider the land area necessary to provide food and other resources for this compact population.
Humans have been a formidable force in destroying the habitats of other organisms. An important question in the future of our species is not only whether we will survive, but at what cost to the other inhabitants of our planet. Considering our difficulty in generalizing an in-group characterization to other ethnicities, it will certainly be a challenge to justify the preservation of natural habitats over the ease of obtaining material comforts. While these conditions may lead to pessimistic views on the condition of humanity and the future of the human species, we have made considerable progress in recognizing our impact on the natural environment.
New technologies are currently under development which may provide more efficient and less resource intense alternatives to the systems in place today. It may take considerably more time to reverse the damaging ecological impact of industrialization, but this is certainly within our capacity. Humans may now begin to realize that they are a highly significant factor in the continued survival and evolution of the species on this planet.
From our perspective, the processes of natural and sexual selection on the evolution of the human species will not result in a "perfect human" being, and it is possible that due to technological advances, the changes resulting from these natural forces has come to a grinding halt. Technological advancement may open another possibility for changes in the human species, that of artificial selection.
With a pace considerably quicker than the selective breeding dreams of the early eugenecists, genetic engineering may soon have the potential to alter human nature. By manipulating the blueprint of life, humans may have the power to select for characteristics at will. With the cloning of mammals a reality and the Human Genome Project well under way, scientists will soon be tinkering with our own genetic code.
It is likely that initial attempts will be trial and error, as in many other areas of science, but a few speculations can be made. Scientists may first try to eliminate "harmful genetic defects," such as Down's Syndrome, and genes predisposing one to poor health conditions. Work bolstering the human immune system may result in an evolutionary arms race between rapidly mutating virii and bacteria, and human designs for resistance.
While the creation of "the perfect human being" may continue to be a subjective notion in the realm of science fiction, the artificial manipulation of the biological basis for evolution may occur in our lifetimes. It has yet to be found whether this ability will prove adaptive in the long run, providing benefits that outweigh its costs.