When you imagine an ideal romantic partner, a burly, hirsute Neanderthal probably doesn't spring to mind. However, groundbreaking new research from the University of Oxford suggests our ancestors might have found them rather appealing, with evidence pointing to intimate encounters that included kissing.
Defining The Kiss: More Than Just Locking Lips
Before tracing the history of kissing, researchers led by postdoctoral scientist Matilda Brindle faced a fundamental challenge: defining what actually constitutes a kiss across different species. Many behaviours resemble kissing but serve entirely different purposes.
Primates often practice premastication, pre-chewing food for their offspring. Ants engage in trophallaxis, exchanging food and fluids mouth-to-mouth. Even tropical French grunt fish lock lips, though this is actually a dominance display known as 'kiss-fighting'.
The team established a clear definition: kissing is non-aggressive, directed, mouth-to-mouth contact between members of the same species that doesn't involve food transfer. This definition excludes accidental interactions or cross-species encounters, focusing instead on genuine intimate contact.
The Ancient History Of Primate Passion
Using this definition, researchers scoured scientific literature for observations of kissing among monkeys and apes from Africa, Asia, and Europe. Their findings revealed that most apes and a handful of monkeys have been observed kissing, with the notable exceptions of Eastern gorillas and small apes like gibbons and siamangs.
The style and purpose of kissing varies significantly between species. Bonobos engage in what can only be described as sensual affairs featuring 'prolonged tongue-tongue interaction'. Other apes use kissing as foreplay or during sex, while across most ape species, kissing serves affectionate, platonic purposes like mother-infant bonding or reconciliation after conflicts.
Through phylogenetic comparative analysis, which combines behavioural data with evolutionary relationships between species, the team reconstructed kissing's history. Their results show that the ancestors of large apes were kissing as far back as 21.5 – 16.9 million years ago, establishing a long evolutionary tradition that continues in most descendant species today.
The Neanderthal Connection: More Than Just Shared Meals
Perhaps the most intriguing finding concerns our ancient cousins, the Neanderthals. The research indicates they were likely partial to a good smooch, which sheds new light on previous discoveries about human-Neanderthal interactions.
Earlier studies revealed that modern humans and Neanderthals shared an oral microbe long after their evolutionary paths diverged. For this transfer to occur, saliva must have been exchanged between the two species. While this could theoretically happen through shared food consumption, when combined with the new evidence that kissing was present in Neanderthals, a more intimate picture emerges.
This possibility gains further support from genetic evidence showing that most people of non-African descent have some Neanderthal ancestry. While kissing doesn't preserve in the fossil record, the cumulative evidence strongly suggests that human-Neanderthal encounters involved more than just practical cooperation.
The research, published on Wednesday 19 November 2025 in The Conversation, fundamentally changes our understanding of both Neanderthal behaviour and the deep evolutionary roots of human intimacy. As Brindle notes, it certainly gives us reason to look at Neanderthals in a new, more romantic light.
