"Sheldrake postulates that knowledge is spread throughout each species through these fields." The root of the problem with Sheldrake's work is right here. Real scientists don't postulate anything, they observe nature, construct models, and perform experiments to test hypotheses. Sheldrake's methodology is not considered sound by most scientists.
Two examples of morphic-field-mediated learning are mentioned, but no references are provided. I have not heard of any credible experiments tending to establish the existence of "morphic fields" and the famous case of the "hundreth monkey" cited by Ken Keyes in his book of that title has been thoroughly debunked. An essay by James Gregory titled "The Hundreth Monkey Revisited," which can be found at http://www.nhne.com/sahundrethmonkey.html, establishes this definitively. (However, "Murphic fields" appear to be real.)
For those interested in paranormal phenomena I recommend the books of Dr. Charles Tart, which are intelligently written and methodologically scrupulous. Many of Dr. Tart's scientific papers on parapsychology and related subjects appear on his Web site, www.paradigm-sys.com/cttart/websites/ctt-science.html.