**Drake's rule**

Drake's rule states that the genome-wide mutation rate is more or less constant across all species — from *E.coli* to the house sparrow.

**Data**

From what I think being Drake's [original paper][1] (table 1, page 4) on the subject (see here) is at the order of $3\times 10^{-3}$. When I look at [this paper][2], I see that the genome-wide mutation rate is roughly around 30 for human. When I look at this paper, they cite some other papers suggesting a genome-wide mutation rate in the order of 0.1 to 1 in multicellular eukaryotes and typically at the order of 1 for vertebrates. Finally, when I look at [this speech][3] (at the 60th minute), it seems however that the genome-wide mutation rate in human is 2.2.

**What is going wrong?**

Do I mix-up different concepts or are there some very contradicting estimates depending on the article we look at? Isn't the genome-wide mutation rate, $U$, which is just the number of de novo mutations transmitted to one offspring on average? What is a correct estimate of $U$ for human for example (1, 2.2 or 30)?


  [1]: http://www.pnas.org/content/88/16/7160.full.pdf+html
  [2]: http://digitalcommons.wayne.edu/humbiol/vol85/iss4/1/
  [3]: https://www.youtube.com/watch?v=jctvV5xrWw4