The number of ancestors you have doubles with each preceding generation, but this is complicated by pedigree collapse.
Here's a breakdown of potential ancestors, assuming no pedigree collapse:
Potential Ancestors by Generation
The theoretical number of ancestors doubles with each generation going back.
| Generation Back from You | Relationship | Ancestors | Cumulative Total Ancestors |
|---|---|---|---|
| 1 | Parents | 2 | 2 |
| 2 | Grandparents | 4 | 6 |
| 3 | Great-grandparents | 8 | 14 |
| 4 | 2nd-great-grandparents | 16 | 30 |
| 5 | 3rd-great-grandparents | 32 | 62 |
| 6 | 4th-great-grandparents | 64 | 126 |
| 7 | 5th-great-grandparents | 128 | 254 |
| 8 | 6th-great-grandparents | 256 | 510 |
| 9 | 7th-great-grandparents | 512 | 1022 |
| 10 | 8th-great-grandparents | 1024 | 2046 |
The Reality of Pedigree Collapse
In reality, the theoretical doubling of ancestors doesn't hold true due to something called pedigree collapse. This occurs when ancestors appear in multiple places in your family tree. It typically happens when families live in the same geographic area for extended periods, leading to intermarriage between relatives. Cousin marriages are a common cause of pedigree collapse.
Because of pedigree collapse, the actual number of unique ancestors you have is less than the theoretical number. The further back in time you go, the more significant the effect of pedigree collapse becomes. Therefore, while you could have 2046 ancestors going back 10 generations, it's much more likely you have significantly fewer unique individuals in those slots.
