Table 1. The relationship between excavation year and the proportion of contaminant clone sequences.
| Proportion of contaminant clone sequences | Excavation Yeara | Correlation | |||
| Sequence fragment | N | Mean (S.E.) | Mean (S.E.) | Spearman's ρ | P-value |
| 16055-16218 | 87 | 0.18 (0.021) | 1946.5 (2.46) | −0.214 | 0.046 |
| 16055-16410 | 48 | 0.27 (0.042) | 1948.8 (3.68) | −0.026 | 0.861 |
| 16209-16410 | 79 | 0.18 (0.024) | 1947.1 (2.39) | −0.26 | 0.021 |
| 16517-160 | 85 | 0.17 (0.023) | 1945.3 (2.5) | −0.505 | <10−6 |
| 16517-334/409 | 19 | 0.26 (0.07) | 1948 (5.74) | −0.533 | 0.019 |
| 183-334/409 | 68 | 0.19 (0.018) | 1947.8 (2.54) | −0.113 | 0.36 |
| All fragments | 386 | 0.19 (0.011) | 1946.9 (1.15) | −0.259 | <10−6 |
a
The range of excavation years was 1880 to 1996 for all sequence fragments, except for 16517-334/409 and 183-334/409, which were 1909 and 1901, respectively.