There are no fossil remains of Stone Age hang gliders or trading records from pre-Columbian stock exchanges, but risk-taking behavior is as old as the sabertooth. Yet what compels modern adventurers to do such foolhardy things as jumping off dizzying cliffs or speculating in Internet stocks Amateur analysts once psychobabbled about a death risk -- an old Freudian cliché that said risk takers were really driven by subconscious feelings of guilt. Nowadays scientists say the real roots of such behavior are as likely to be found in the convoluted chemistry of the genes as in the id or the superego.
Long before genes were discovered, Darwin suspected that behavior was at least partly inherited. But only recently have scientists working in the burgeoning field of behavioral genetics begun to link specific stretches of DNA with personality traits. Studying the DNA of subjects who were identified as curious and excitable -- two of the common characteristics of those who lo
A. drive in advance
B. help first
C. make liable
D. regulate beforehand
There are no fossil remains of Stone Age hang gliders or trading records from pre-Columbian stock exchanges, but risk-taking behavior is as old as the sabertooth. Yet what compels modern adventurers to do such foolhardy things as jumping off dizzying cliffs or speculating in Internet stocks Amateur analysts once psychobabbled about a death risk -- an old Freudian cliché that said risk takers were really driven by subconscious feelings of guilt. Nowadays scientists say the real roots of such behavior are as likely to be found in the convoluted chemistry of the genes as in the id or the superego.
Long before genes were discovered, Darwin suspected that behavior was at least partly inherited. But only recently have scientists working in the burgeoning field of behavioral genetics begun to link specific stretches of DNA with personality traits. Studying the DNA of subjects who were identified as curious and excitable -- two of the common characteristics of those who lo
A. appreciative
B. objective
C. negative
D. protective
The fossil remains of the first flying vertebrates, the pterosaurs. have intrigued paleontologists for more than two centuries, How such large creatures, which weighed in some eases as much as a piloted hang-glider and had wingspans from 8 to 12 meters, solved the problems of powered flight, and exactly what these creatures were — reptiles or birds — are among the questions scientists have puzzled over.
Perhaps the least controversial assertion about the pterosaurs is that they were reptiles. Their skulls, pelvises, and hind feet are reptilian. The anatomy of their wings suggests that they did not evolve into the class of birds. In pterosaurs a greatly elongated fourth finger of each forelimb supported a wing like membrane. The other fingers were short and reptilian, with sharp claws. In birds the second finger is the principal strut of the wing, which consists primarily of feathers. If the pterosaurs walked on ail fours, the three short fingers may have been
A. enormous wingspans of the pterosaurs enabled them to fly great distances
B. structure of the skeleton of the pterosaurs suggests a close evolutionary relationship to hats
C. fossil remains of the pterosaurs reveal how they solved the problem of powered flight
D. pterosaurs were reptiles
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