When you take a decades-long perspective on scientific milestones, you soon realize how much the current pioneers owe to their predecessors. Take medicine, for example: The genetic war on diseases such as cancer really ramped up in the 1970s, and is just now beginning to yield itsrichestpayoffs.
The '70s also saw the discovery of Lucy, the 3.2 million-year-old hominid fossil that opened a new chapter in the scientific story about human origins. This year, another fossil from Ethiopia, nicknamed Ardi, added yet another chapter to the tale just this year.
In the '70s, NASA's sent twin Viking missions to Mars and the Voyager spacecraft to Saturn and our solar system's other other planets. In 2009, NASA's twin Mars rovers and the Cassini orbiter are turning up new wonders in those old interplanetary neighborhoods.
These science sagas from the 1970s are part of a larger timeline of 50 scientific milestones from the past 50 years, drawn up for the 50th anniversary of the Council for the Advancement of Science Writing:
1970
13. Oncogenes: First cancer-causing gene is discovered in a chicken retrovirus. In 1976, J. Michael Bishop and Harold Varmus described the mechanism by which proto-oncogenes mutate and give rise to cancer - a discovery that earned them the Nobel Prize in 1989.
1972
14. Medical scanners: First CT scanner is created. Computerized tomography X-ray scanners not only revolutionized medical imaging, but also presaged other imaging techniques such as magnetic resonance (MRI and functional MRI) as well as positron emission tomography (PET). Such techniques have been put to wide application in medical diagnosis and neuroscience, and even archaeology and paleontology.
15: Recombinant DNA: Stanford biochemist Paul Berg creates the first recombinant DNA molecule, pointing the way to genetically modified organisms and gene-based medical therapies. The technique proved so powerful and controversial that it led to a 1975 conference at California's Asilomar Conference Center, where scientists voluntarily agreed on research restrictions. The Asilomar conference itself stands as a milestone in scientific accountability.
1974
16. Human ancestors: Paleoanthropologist Donald Johanson discovers the 3.2 million-year-old fossil skeleton of a human ancestor dubbed "Lucy" in Ethiopia. The australopith find serves as the best-known milestone in a long line of hominid discoveries also including the Laetoli footprints in Tanzania (1976), the Toumai skull in Chad (2002) and Ardipithecus in Ethiopia ("Ardi" found in 1994, characterized in 2009).
17. Countering the ozone threat: Chemists F. Sherwood Rowland and Mario Molina propose that chlorofluorocarbons may affect Earth's ozone layer - a hypothesis that was borne out over the following decade, particularly with the identification of the Antarctic ozone hole in 1985. Concerns about CFCs led to a phase-out of their production mandated by the 1987 Montreal Protocol. The Rowland-Molina research and its impact set a precedent for the current debate over greenhouse-gas emissions.
1976
18. Pictures from other planets: NASA's Mars Viking probes land on Mars and send back the first color pictures from another planet. The twin missions follow up on the Soviet Venera 9 and 10 missions, which transmitted black-and-white images from Venus in 1975.
1977
19. Deep-sea life: Biologists discover a rich ecosystem surrounding deep-sea hydrothermal vents along the Galapagos Rift. The discovery dramatically changed scientists' views on the conditions required for life on Earth, sparked new ideas about the potential undersea origins of life and led astrobiologists to consider the possibility of life in extraterrestrial settings such as the subsurface oceans of Europa (a moon of Jupiter) and Enceladus (a moon of Saturn).
20. Farthest frontier: NASA launches the twin Voyager probes, following up on the Pioneer interplanetary missions with a grand tour of the solar system. Both craft flew past Jupiter and Saturn. Voyager 2 flew past Uranus and provided the first up-close look at Neptune. Voyager 1 is now the farthest-flung object ever made by humans. Both Voyager spacecraft probes carried a "Golden Record" with recordings of Earth imagery, sounds, speech and music.
1978
21. Test-tube babies: The first baby conceived through in-vitro fertilization is born in England. The method is a boon to couples with fertility problems. Since then, an estimated 3.5 million "test-tube babies" have been born using assisted reproductive technology. But the method is not without controversy, as illustrated by the furor over the birth of octuplets to "Octomom" Nadya Suleman in 2009.
22. Data encryption: MIT's Ron Rivest, Adi Shamir and Leonard Adleman describe the RSA public-key encryption method, which draws upon prime factorization to provide a means of secure communications. The encryption method serves as the foundation for applications ranging from military communications to Internet commerce.
You can see the full timeline on CASW's site. I'm also looking for suggestions on potential scientific milestones for the next 50 years. Monday's installment on the '60s has already generated some great ideas, ranging from medical nanobots to smart flying machines and amusement parks in space. Feel free to add your own flights of fancy as comments below.