A few examples:
For an Anglo-American person living in New York City, their ancestors might primarily be English, Anglo-Saxon, Proto-Germanic, Proto-Indo-European etc. while their predecessors will be Dutch, Lenape/Delaware, Paleo-Amerindian etc.
For a French person living in Paris, their ancestors might primarily be Roman, Proto-Itallic, Proto-Indo-European etc. while their predecessors will be Roman, Celtic, Bell-Beaker, Anatolian Neolithic, Western Hunter Gatherer, Cro Magnon, Neanderthal etc.
For a Taiwanese person living in Taipei, their ancestors might primarily be Min Chinese, Proto-Sinitic, Proto-Sino-Tibetan etc. while their predecessors will be Dapenkeng, Changbin, Australo-Papuan, Denisovan etc.
1,000A few problems here...for your French example, you've listed "Roman" as both "ancestor" and "predecessor" options, but there's no "both" option in the poll.
Also—why would someone not have Celtic ancestors, in Paris? The Romans didn't displace the Gauls, they were not exterminated. Someone could even have fully Gallic ancestry, with no Romans at all. So for them, "Celtic" would be the ancestors, & "Roman" the predecessors.
& then we come to the larger problem, how you are defining "ancestor" and "predecessor." What if someone of Lenape descent is living in NYC? How do they vote?
What determines which groups get to count as "predecessor?" English people have lived in NYC for centuries. Why aren't they "predecessor?" Why is "Paleo-Amerindian" a predecessor group, but "Proto-Indo-European" an ancestor group? What differentiates them? The whole thing is very confused.