Footnotes

• Contributors No financial support was needed, and I have no conflicts of interest. Figures were created by myself (Figure 1) or modified from sources under Creative Commons Attribution 4.0 license and attribution given as specified (Figure 2) and then both adapted using other texts as cited.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests None declared.

• Provenance and peer review Not commissioned; internally peer reviewed.