キスの進化的研究
Hello everyone, SCIENSPOT is a podcast that shines a spotlight on the latest scientific
technology from Japan. Your host is REN from SCIEN-TALK. Today we are talking about a study
that reconstructs the evolutionary origins of kissing, a common but mysterious behavior
found across the animal kingdom. This research was conducted by scientists from the University
of Oxford. Kissing poses an evolutionary puzzle. It does not clearly aid survival or reproduction,
yet it carries the potential cost of disease transfer. To understand its function, the
team used a non-anthropocentric approach and first rigorously defined kissing. Their definition
of kissing is a non-agonistic, directed oral-oral contact involving some movement of the lips
and no food transfer. This behavior is observed not just in humans, but in most large apes
and some monkeys, as well as species as diverse as polar bears and avatars. The team's primary
goal was to map out the evolutionary history of this behavior. They compiled observational
data across primates and used Bayesian phylogenetic methods. This is a sophisticated statistical
tool that uses the evolutionary tree to estimate when a specific trait, like kissing, first
evolved and how many times it may have been lost, gained, or gained across different lineages.
The analysis suggests that mouse-to-mouse kissing likely first evolved in the ancestors
of large apes, sometime between 21.5 and 16.9 million years ago. Because humans, chimpanzees,
キスの起源と機能
and bonobos like kiss, the researchers concluded that their closest common ancestor likely
engaged in the behavior. This study also concluded that Neanderthals, our closest existing human
relatives, most likely kissed. This is supported by previous microbiome research. This research
showed that modern humans and Neanderthals share certain oral microbes long after their
species diverged, meaning they were exchanging saliva, possibly through kissing, parental
care, or food sharing. So, if it's risky, why do we kiss? Several adaptive functions
are hypothesized. First thing is mate evaluation. Sexual kissing may allow partners to evaluate
mate quality, general health, genetic fitness, or even the female's menstrual cycle phase
through olfactory signals. It acts as a health quick check. Second thing is affiliation and
bonding. Both sexual and platonic kissing serve the affiliate purpose in social species,
helping to strengthen bonds, mitigate tension, and navigate relationships. The researchers
suggest that kissing may have been excerpted or repurposed from a parental behavior called
pre-mastication. Pre-mastication is the act of a parent pre-chewing food and then transferring
it mouth-to-mouth to an infant who cannot eat chew-solid food. Since pre-mastication
involves the necessary mouth-to-mouth contact and lip movement, it is a strong candidate
for the ancestral behavior that was adapted into what we now recognize as kissing. This
research shows that kissing is not a recent, culturally specific human invention, but rather
キスの進化の定義
an ancient and phylogenetically conserved trait with the great ape lineage that began
over 21 million years ago. By providing a clear definition and evolutionary framework,
this study opens the door for future research to definitively answer the fundamental question,
what is the adaptive function of a kiss?
That's all for today SciencePod. This podcast is broadcast in both Japanese and English.
I'd love for you to listen to the podcast and post your thoughts with the hashtag SciencePod.
Thank you for listening and see you next time.
