Alu elements belonging to the previously identified "young" subfamilies are 
thought to have inserted in the human genome after the divergence of humans from 
non-human primates and therefore should not be present in non-human primate 
genomes. Polymerase chain reaction (PCR) based screening of over 500 Alu 
insertion loci resulted in the recovery of a few "young" Alu elements that also 
resided at orthologous positions in non-human primate genomes. Sequence analysis 
demonstrated these "young" Alu insertions represented gene conversion events of 
pre-existing ancient Alu elements or independent parallel insertions of older 
Alu elements in the same genomic region. The level of gene conversion between 
Alu elements suggests that it may have a significant influence on the single 
nucleotide diversity within the genome. All the instances of multiple 
independent Alu insertions within the same small genomic regions were recovered 
from the owl monkey genome, indicating a higher Alu amplification rate in owl 
monkeys relative to many other primates. This study suggests that the majority 
of Alu insertions in primate genomes are the products of unique evolutionary 
events.