Multiple realities
(covers information from several alternate timelines)
A baby on Gaia sucking his thumb
Thumbsucking was an act of self-soothing typically done by babies and young children.
In 2270, a de-aged Arex sucked his thumb. (TAS: "The Counter-Clock Incident")
In an alternate timeline on the planet Gaia, a young descendant of Benjamin Sisko sucked his thumb while meeting his ancestor. (DS9: "Children of Time")