Y-chromosomal Adam doesn't refer to the oldest homo sapien. Rather, it refers to the original male homo sapiens who established a continuous patriline of male descendants (father-to-son) who've passed on their y-chromosome down to the present day. There were likely many forebears before him who've passed on their DNA to present-day descendants, but it isn't genetically traceable because the y-DNA patriline was broken at various points.
The same applies to mitochondrial Eve. She very likely wasn't one of the first female homo sapiens. But she was the most recent female ancestor who established a traceable mother-to-daughter mitochondrial DNA lineage which still exists. There were almost certainly plenty of other female homo sapiens who preceded her, and who have descendants today, but at some point along the way, the continuous mitochondrial mother-to-daughter matriline was broken, and so their DNA can't be traced back to them.
Regular DNA recombines with each new generation, so after many generations have passed, it's no longer traceable. But y-chromosome DNA (passed on only by males) doesn't recombine, so it's traceable in its pure state from male ancestors down through the generations. X-chromosomal DNA can be passed on by both parents, so it isn't traceable. However, the mitochondria in the female ova are passed on in the pure state, so the matriline may be traced. Each mother, through her ova (eggs), passes on her mitochondrial DNA to all her children, sons and daughters. But only the daughters, through their ova, pass it on to their own children. Thus it's traceable in the female line, down through the generations. The mitochondria of males will tell which matriline they descend from, but they won't transmit it to their own descendants, because it's only contained in the ova.
Y-chromosomal Adam, and Mitochondrial Eve, in all likelihood, lived at different times and places, and had no relationship with each other.