3804 different reconstructions (sometimes with multiple constructions for a given family). In contrast to traditional comparative linguistics, the researchers did not attempt to "prove" any given pairing as cognates (based on similar sounds), but rather treated each pairing as a binary random variable subject to error. The set of possible cognate pairings was then analyzed as a whole for predictable regularities. Words were separated into groupings based on how many language families appeared to be cognate for the word. Among the 188 words, cognate groups ranged from 1 (no cognates) to 7 (all languages cognate) with a mean of 2.3 ± 1.1. The distribution of cognate class size was positively skewed − many more small groups than large ones − as predicted by their hypothesis of variant decay rates. Words were then grouped by their generalized worldwide frequency of use, part of speech, and previously estimated rate of replacement. Cognate class size was positively correlated with estimated replacement rate (r=0.43, p<0.001). Generalized frequency combined with part of speech was also a strong predictor of class size (r=0.48, p<0.001). Pagel et al. conclude "This result suggests that, consistent with their short estimated half-lives, infrequently used words typically do not exist long enough to be deeply ancestral, but that above the threshold frequency words gain greater stability, which then translates into larger cognate class sizes." Twenty-three word meanings had cognate class sizes of four or more. Words used more than once per 1,000 spoken words (χ2=24.29, P<0.001), pronouns (χ2=26.1, P<0.0001), and adverbs (χ2=14.5, P=0.003) were over-representing among those 23 words. Frequently used words, controlled for part of speech, were 7.5 times more likely (P<0.001) than infrequently used words to be judged as cognate. These findings matched their a priori predictions about word classes more likes to retain sound and meaning over long periods of time. The authors write "Our ability to predict these words independently of their sound correspondences dilutes the usual criticisms leveled at such long-range linguistic reconstructions, that proto-words are unreliable or inaccurate, or that apparent phonetic similarities among them reflect chance sound resemblances." On the first point, they argue that inaccurate reconstructions should weaken, not enhance, the signals. On the second, they argue that chance resemblances should be equally common across all word usage frequencies, in contrast to what the data shows. The team then created a Markov chain Monte Carlo simulation to estimate and date the phylogenetic trees