Female baboons' bodies can 'screen out' unsuitable sperm - study

It's about hidden physiological processes.

Details

The study was conducted on a group of 13 baboons - nine females and four males.

Scientists studied how the organism of females reacts to the sperm of different partners.

They found that after mating, the conditions in the vagina change:

• if the partner is genetically similar, the environment becomes more acidic
• which reduces the survival rate of sperm
• with genetically more "different" partners, the conditions remain more favourable

In addition, there were changes in gene activity.

This was particularly true of the immune system:

• with an "unsuitable" partner, the inflammatory response increased
• mechanisms that could prevent fertilisation were activated

During the period of maximum fertility, on the contrary, immune activity decreased to allow sperm to survive.

Why it matters

The results show that reproduction is a more complex process than just mating.

The scientists note:

• the body can influence the likelihood of conception
• genetic compatibility plays an important role
• such mechanisms may favour genetic diversity

This is about physiological reactions, not "conscious choice".

Background

This mechanism is known as cryptic female choice.

It has previously been observed in small animals, but there is limited data in primates.

Source

The study is based on analysis of physiological and genetic responses in 13 baboons after mating, including measurements of pH and gene activity. The work is published in PLOS Biology (2026).