The human species may be more than 100,000 years old but the bulk of its numerical growth has come in just the last few decades: 2.6 billion of today's 5.6 billion people have been born since 1960.
Humans have only been around for 50 years.
( z1 exist :ARG1 ( z2 human ) :duration ( z3 temporal-quantity :quant 50 :unit ( z4 year ) :mod ( z5 only ) ) )