Overview: Life Sciences 1950-present

Background: Advances between 1900-1949

Early in the twentieth century the rediscovery of Gregor Mendel's (1822-1884) work on heredity in pea plants led to the development of the field of genetics. In the 1940s Oswald Avery (1877- 1947) and his research associates at the Rockefeller Institute in New York found that DNA was the genetic material, the chemical information passed on from one generation to the next, that determines traits in all species. At about the same time, a group of researchers from a number of different areas of biology—zoology, ecology, genetics, and paleontology—developed what came to be called the Modern Synthesis, the updating of Charles Darwin's (1809-1882) theory of evolution to incorporate the new discoveries in genetics and other areas of biology. It was also during the first half of the century that ecologists developed mathematical methods for describing changes in populations over time, techniques for sampling populations and for studying interactions between species, and concepts such as food chains and webs. The second half of the twentieth century saw further development in these fields, with greater knowledge of DNA influencing almost all areas of biology.

1950-present: Molecular Biology and Genetics

Certainly the most important event in biology in the post-1950 period was the discovery of the structure of DNA by James Watson (1928- ) and Francis Crick (1916- ) in 1953. This opened the way for a thorough investigation of precisely how a gene, a piece of DNA containing the information to make one cellular substance, is controlled, and how the information in the genes is used to make proteins, the molecules that are key to the functioning of cells. Through the 1950s and 1960s biologists worked out the steps in this process, called protein synthesis, and learned a great deal more about cellular structures including the fundamentals of gene regulation. Much of this research was done on bacteria and viruses, the simplest forms of life. It was only in the 1970s that techniques were developed for studying the genes of plants and animals, leading ultimately to the Human Genome Project, a massive effort to discover the complete human genetic makeup.

With recombinant-DNA techniques, it became possible to isolate specific genes and to insert them into the DNA of other organisms. This type of genetic engineering has blossomed, making possible the large-scale production of insulin and many other human proteins. It has also revolutionized agriculture and the food industry, with the insertion of genes for accelerated growth into animals and for insect and herbicide resistance into plants. In addition, new techniques developed since the 1960s make it much easier to analyze genetic differences between individuals; studies have unearthed a great deal of genetic diversity within species and races, calling into question the whole concept of race as a biological entity. Finally, in 1997 the first clone of an adult mammal, a sheep named Dolly, was born. Since then a number of other mammalian species, including mice, monkeys, and cattle, have been cloned, leading to a heated debate on the ethics of cloning humans.

Ecology and Environmental Science

Since the 1950s ecologists have become more aware of the complexity of ecosystems and the difficulty of predicting change. They continue to debate whether species diversity makes ecosystems more or less stable and to search for better mathematical models to describe the structure of ecosystems, of how the organisms within an ecosystem interact with each other. Environmental science developed in the 1960s in response to an increasing awareness of environmental deterioration, sparked in part by the writings of such activists as Rachel Carson (1907-1964), whose Silent Spring (1961) dealt with the dangers of pesticides. Late in the century "biodiversity" became an important concept, marking a shift away from efforts to save individual species from extinction to saving habitats and thus a diversity of species. Since the 1980s concerns have also grown about the destruction of the ozone layer in the upper atmosphere that screens out ultraviolet radiation and about global warming, the apparent increase in average temperatures that seems to be leading to climatic changes that influence the species composition of ecosystems.

There has also been mounting worry over the continued destruction of rainforests and wetlands and the relationship between environmental destruction and the emergence of new infectious diseases. With the destruction of their habitats, animals are forced into more contact with humans and thus are more likely to transmit animal diseases to them. There is also growing concern that genetically altered crops will have significant environmental impact as genes move from crop plants into related wild species. At the same time, many farmers are attempting to reduce the environmental impact of farming by using fewer pesticides and herbicides and by adopting methods that conserve soil and lessen water pollution.

Evolution

At the end of the twentieth century evolution remains the unifying concept that underlies all of biology. While the Modern Synthesis is still central to most biologists' thinking on evolution, a number of newer ideas have caused some modification of it. These include punctuated equilibrium, the concept that change in species does not necessarily occur gradually, but that a period of rapid change may be followed by long intervals with little modification. Debates among biologists about the mechanisms of evolution, though not about the fact of its occurrence, have made it easier for creationists to challenge the theory. Creationists see the idea of the creation of living things by a divine being as one that should be given at least equal standing with evolution in the schools, despite the fact that the past 50 years have seen the discovery of much new evidence for evolution. Rich fossil beds in China and Mongolia have revealed the existence of many previously unknown dinosaur species as well as much new information on the origin of mammals and birds. A great deal of evidence has been discovered supporting the theory that the final extinction of the dinosaurs was due to a comet hitting Earth, causing massive climate changes that the dinosaurs could not survive. Another important trend has been the discovery of many new fossils of early humans and their ancestors, making it obvious that the human family tree has had many branches; modern humans are only one of several lines and the only one to survive to the present day.

Neurobiology and Behavior

Over the past 50 years the study of primates, the closest living relatives to humans, has grown significantly, with a number of researchers including Jane Goodall (1934- ) and Dian Fossey (1932-1985) dedicating themselves to behavior studies of specific ape species. In the 1950s Noam Chomsky (1928- ) developed the idea that human language acquisition is biologically encoded; this sparked research on the language abilities of apes. In terms of humans, Alfred Kinsey (1894-1956) published landmark studies on sexual behavior that others have since added to and amended. Neurobiology has also flourished, as major discoveries have been made on brain chemistry and the functioning of nerve cells. New imaging techniques such as PET scans have made it possible to study brain activity of normal subjects carrying out everyday tasks such as reading and puzzle-solving.

The Future

In the next half century it is clear that continued exploration of the genes and how they are controlled will lead to new drugs, new foods, and new knowledge about the human body and its diseases. There will also be increased efforts to understand and preserve the great diversity of life on Earth, especially as threats to that diversity intensify. The exploration of our evolutionary past will continue, as biologists search for new fossil evidence while at the same time using genetic analysis to discover relationships among present-day species. In the past 50 years biology has become a much more complex science with a growing impact on our lives, and that trend is likely to continue in the near future.

ROBERT HENDRICK