Objective:

To investigate the evolutionary history of kissing in large apes and its potential occurrence in Neanderthals, highlighting the significance of understanding this behavior in our closest relatives.

Key Findings:

• Kissing likely evolved in the common ancestor of large apes between 21.5 and 16.9 million years ago, indicating a deep evolutionary root.
• Neanderthals had a high probability of engaging in kissing (posterior probability of 0.843), suggesting behavioral similarities with modern humans.
• Kissing is a phylogenetically conserved trait within large apes, with possible independent origins in Afro-Eurasian monkeys, highlighting its evolutionary significance.

Interpretation:

Kissing is an ancient behavior that has been retained across hominid lineages, suggesting deep evolutionary roots and potential social functions.

Limitations:

• Sparse and uneven data across taxa, often from captive populations, limits the reliability of findings.
• Binary classification of kissing does not account for variations in frequency, context, and social function, including cultural differences in humans.
• Limited data outside large apes restricts phylogenetic power and hypothesis testing, necessitating caution in drawing broad conclusions.

Conclusion:

Kissing is a significant behavioral trait with evolutionary implications, though further research is needed to address data limitations, particularly in understanding its cultural variations.