let them ask. use my response back at them.
"What have you remained since a fertilized cell?
Ever changing body with same chromosomes as the nucleus of every fertilized cell became the body's brain by birth and at death still same chromosomes within similar DNA of the same species. That covers ancestral lineages combine to each ancestor living today. No missing links possible unless using relative tie logistical facts.
No conception, no ancestor, no next generation gap, extinction for the ancestral lineage so far per reproduction present, universal constant.