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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

By Walter F. Bodmer and Luigi Luca Cavalli-Sforza

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

By Robert S. Dietz and John C. Holden

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

By Howard Rasmussen and Maurice M. Pechet

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

By Barry N. Taylor, Donald N. Langenberg and William H. Parker

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

By Richard W. Young

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

By F. Herbert Bormann and Gene E. Likens

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

By Ivan Berenyi

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

By Otto Mayr

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