Science is not always a direct ascent toward the truth

Despite the meticulous efforts of those who practice it, science sometimes proceeds in lurches and false starts. In some cases, scientific ideas that dominated a particular time were later recognized as inaccurate or incomplete.

• Before Galileo challenged the system, geocentrism was the rule. The geocentric model of the Universe, shown to the right, persisted for centuries. Eventually, people came to accept that the Earth is not the center of the Universe.
• Speciation was first described as a gradual process, but in recent years it has become clear that under some conditions speciation can occur relatively rapidly.
• Alfred Wegener’s ideas about continental drift were not taken seriously until viable mechanisms for moving continents began to be recognized.

Science corrects itself

Sometimes people make mistakes. Occasionally scientists are swept up in a current of ideas that leads them astray. But errors, misconceptions, and misdirections are corrected by the scientific community itself. Sometimes corrections take years, decades, or even centuries. Improved understanding may result from new technology or changing perspectives, but sooner or later a closer approximation of the truth appears. The fact that old hypotheses fall and new ones take their place does not mean that science is invalid as a way of gathering knowledge. Plasticity of thought is the very essence of the scientific process.

For example, within the past 100 years, textbooks have gone from grouping all living things into two kingdoms, to portraying the connectedness of life as three domains.

Science is a human endeavor

All human frailties are present among scientists. These include:

• Falling in love with one’s own hypothesis and becoming so attached to it that one refuses to consider new or conflicting data. The cold fusion episode of the 1990s, which implied unlimited energy from a low-temperature version of hydrogen fusion, should serve as a warning to would-be instant scientific heroes.
• Being drawn in by preconceptions. A century ago people visualized the human ancestor with bent legs, club in hand, but with enough gray matter to make tools and control fire. “Cave man” cartoons continue to preserve this misperception. But, discoveries in recent decades, such as Australopithecus afarensis, show that even very early human ancestors stood upright, had feet and legs much like ours, but had brains relatively little larger than those of chimpanzees. Science, sooner or later, overcomes prejudices and misapprehensions that are due to cultural influences and personal bias. That is one of the powers of the scientific enterprise.