A researcher is trying to figure out if more women are deciding not to have children because of changes in economics and birth control, or if genetic changes are affecting choices and goals.

Lonnie Aarsen of Queen's University in Canada said the trend of childlessness in developed countries will ease because of biological evolution, despite the fact that women with more financial freedom may decide to pursue leisure and other personal goals, not parenthood.

She said this is because the women who leave the most descendants will be those with an intrinsic drive for motherhood. Over time, she suggests, those genetic traits that influence women away from motherhood will become less prominent.

Aarssen predicted an increased desire for marriage and having children in both men and women within the next few generations.

Aaarsen's paper is published in the journal Oikos.