| No. of generations to D → generation length, years ↓ | 1 | 4 | 40 | 400 | 4,000 | 40,000 |
| 25 | 25 | 100 | 1000 | 10,000 | 100,000 | 1,000,000 |
| 100 | 100 | 400 | 4000 | 40,000 | 400,000 | 4,000,000 |
| 1000 | 1000 | 4000 | 40,000 | 400,000a | 4,000,000 | 40,000,000 |
| 10,000 | 10,000 | 40,000 | 400,000 | 4,000,000 | 40,000,000 | 4 ×108 |
| 100,000 | 100,000 | 400,000 | 4,000,000 | 40,000,000 | 400,000,000 | 4 ×109 |
| 1,000,000 | 1,000,000 | 4,000,000 | 40,000,000 | 400,000,000 | 4,000,000,000 | 4 ×1010 |