AN INTRODUCTORY ORIENTATION 7 
will become impressed, if he has not been so before, with the 
numerous pitfalls into which the student of human evolution is 
liable to fall. The literature on the subject is full of conclusions 
based on inadequate evidence, yet put forth with a confidence 
which in itself should engender a suspicion of their soundness. 
But the most disappointing feature of the situation is the dearth 
of facts upon which safe deductions can be based. Demographi- 
cal statistics have been kept only for a relatively short period of 
time; and anthropometric data have not been gathered on a scale 
sufficiently extensive, or over a period sufficiently long, to give us 
an idea of the trend of development in any considerable group of 
men. Data compiled at different times and places are often not 
comparable for want of common standards. If we wish to deter- 
mine, in what ways the population of any country has been 
changed we encounter almost insuperable difficulties. The 
Parliamentary Committee appointed a few years ago to investi- 
gate the alleged physical deterioration of the people of Great 
Britain, after making an exhaustive enquiry, could come to no 
conclusion as to whether such deterioration had actually occurred. 
Of course this result is of little value in proving the absence of 
physical degeneracy in recent times. It is perfectly consistent 
with the view that such degeneration has even been rapid. It is 
simply a confession that the data are insufficient for the solution 
of the problem. 
But if we are lacking in records which tell us in what direction 
human beings have actually been changed, we can at least ascer- 
tain something of the action of the forces which are now at work 
in modifying the inherited qualities of the race. We can observe 
in a measure how things are actually going on. We can trace the 
way in which hereditary traits are transmitted; we can study at 
first hand the action of natural selection in eliminating ill adapted 
strains of humanity; we can determine the relative degrees of 
rapidity with which different stocks reproduce themselves, and 
we can ascertain something of the action of the various selective 
forces which have arisen as a result of the development of human 
institutions. Where the data which are being accumulated are 
