Intelligence and Race
Do the differences in I. Q. scores between blacks and whites have a genetic basis? Two geneticists, reviewing the evidence, suggest that the question cannot be answered in present circumstances
Volume 223, Issue 4
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Features
The Breakup of Pangaea
Pangaea is the single land mass that is believed to have given rise to the present continents. Its outline has now been plotted and its further disruption has been projected into the future
Calcitonin
This recently discovered thyroid hormone plays an important role in metabolism: it inhibits the breakdown of bone and thus keeps the calcium in the blood from reaching an excessively high level
The Fundamental Physical Constants
Experiments designed to redetermine the numerical values of these quantities to ever greater levels of accuracy can yield information concerning the overall correctness of the basic theories of physics
Visual Cells
The rod and cone cells are exquisitely sensitive, yet they are also durable. It turns out that rods steadily regenerate the thin disks containing visual pigment. Cones renew themselves in another way
The Nutrient Cycles of an Ecosystem
When all vegetation was cut in a 35-acre watershed in an experimental forest in New Hampshire, the output of water and nutrients increased. The experiment illustrates ecological principles of forest management
Computers in Eastern Europe
Energetically trying to catch up in computer technology, the U.S.S.R. and six eastern European countries have set themselves the goal of building 33,000 machines by 1975
The Origins of Feedback Control
The evolution of the concept of feedback can be traced through three separate ancestral lines: the water clock, the thermostat and mechanisms for controlling windmills