When I first met the Ikpeng, a few weeks after their rescue by indigenists, their population was very sparse. The 56 individuals who arrived alive at the Leonardo Villas-Bôas post were quickly reduced to 50, because of an accidental death and five deaths from diseases. By the end of 1969, however, the births increased and when I returned there, in 1972, the Ikpeng had a total population of 62.

The population curve of the Ikpeng before the attack of the Wauja, which marked the beginning of their decline, was relatively stable, given that the confrontations with other groups did not result in many deaths and probably they hadn't yet been exposed to viral infections against which they had no immunity. Thus, from 1932 to 1952, according to a series of sources, the Ikpeng had an average population of 148 people.

If we investigate the facts regarding this brutal decline during the 1960s, when the population was reduced by more than half, we clearly perceive that mortality by disease was far greater than mortality by violence. But, in the following decades, there was an effective demographic recovery and today, the Ikpeng total 315 individuals.