House Bill 291, introduced in the Missouri House of Representatives on January 23, 2013, would, if enacted, require "the equal treatment of science instruction regarding evolution and intelligent design," according to the legislature's summary of the bill. The equal treatment provision would apply to both public elementary and secondary schools and to "any introductory science course taught at any public institution of higher education" in Missouri.

HB 291's text is about 3000 words long, beginning with a declaration that the bill is to be known as the Missouri Standard Science Act, followed by a defectively alphabetized glossary providing idiosyncratic definitions of "analogous naturalistic processes," "biological evolution," "biological intelligent design," "destiny," "empirical data," "equal treatment," "hypothesis," "origin," "scientific theory," "scientific law," and "standard science."

Among the substantive provisions of the bill, applying both to Missouri's public elementary and secondary schools and to introductory science courses in public institutions of higher education in the state: "If scientific theory concerning biological origin is taught in a course of study, biological evolution and biological intelligent design shall be taught. Other scientific theory or theories of origin may be taught."

For public elementary and secondary schools, HB 291 also provides, "If scientific theory concerning biological origin is taught in a textbook, the textbook shall give equal treatment to biological evolution and biological intelligent design." After the bill is enacted, new textbooks purchased for the public schools will have to conform to the equal treatment requirement. A committee will develop supplementary material on "intelligent design" for optional interim use.

HB 291 is apparently a descendant of HB 911 in 2004, which was also dubbed the Missouri Standard Science Act, began with a glossary of the same eleven terms (and also "extrapolated radiometric data"), would have required equal treatment of "intelligent design" in the public elementary and secondary schools (although not in public higher education), and would have required textbooks to conform to the equal treatment requirement.

HB 911 was widely criticized, including by the Science Teachers of Missouri. A sequel bill, HB 1722, also introduced in 2004, contained the same language as HB 911, but omitted provisions that would have required the text of the bill to be posted in high school science classrooms and that would have enabled the firing of teachers and administrators who failed to comply with the law. Both bills died when the legislative session ended.

In 2012, HB 1227, also dubbed the Missouri Standard Science Act, was introduced by Rick Brattin (R-District 55). In discussing HB 1227 with the Kansas City Star (January 14, 2012), Brattin insisted that his bill was not about religion, but was also quoted as saying, "I keep pointing to a Gallup poll that shows 90 percent of Americans believe in a higher power." HB 1227 died in committee when the legislature adjourned in May 2012.

Brattin is the main sponsor of HB 291, which is identical to HB 1227 in 2012; its cosponsors are Andrew Koenig (R-District 99) and Kurt Bahr (R-District 102), both of whom were cosponsors of HB 1227. HB 291 is the sixth antievolution bill of 2013, joining Colorado's HB 13-1089, Missouri's HB 179 (with Brattin, Koenig, and Bahr among its cosponsors), Montana's HB 183, and Oklahoma's HB 1674 and SB 758.