Monsanto Co. started an agricultural revolution with its "Roundup Ready" seeds, genetically modified to resist the effects of its blockbuster herbicide called Roundup. That ability to kill weeds while leaving desirable crops intact helped the company turn Roundup's active ingredient, the chemical glyphosate, into one of the world's most-used crop chemicals. When that heavy use raised health concerns, Monsanto noted that the herbicide's safety had repeatedly been vetted by outsiders. But now there's new evidence that Monsanto's claims of rigorous scientific review are suspect.