Editing Natural selection (section)

==Arms races==
[[File:Antibiotic resistance.svg|thumb|upright|Selection in action: [[Antimicrobial resistance|resistance to antibiotics]] grows through the survival of individuals less affected by the antibiotic. Their offspring inherit the resistance.]]
{{Further|Antimicrobial resistance}}

Natural selection is seen in action in the development of [[Antimicrobial resistance|antibiotic resistance]] in [[microorganism]]s. Since the discovery of [[penicillin]] in 1928, [[antibiotics]] have been used to fight bacterial diseases. The widespread misuse of antibiotics has selected for microbial resistance to antibiotics in clinical use, to the point that the [[Methicillin-resistant Staphylococcus aureus|methicillin-resistant ''Staphylococcus aureus'']] (MRSA) has been described as a "superbug" because of the threat it poses to health and its relative invulnerability to existing drugs.<ref>{{cite news |last1=Harvey |first1=Fiona |author-link=Fiona Harvey |last2=Carson |first2=Mary |last3=O'Kane |first3=Maggie |last4=Wasley |first4=Andrew |date=18 June 2015 |title=MRSA superbug found in supermarket pork raises alarm over farming risks |url=https://www.theguardian.com/society/2015/jun/18/mrsa-superbug-in-supermarket-pork-raises-alarm-farming-risks |work=[[The Guardian]]}}</ref> Response strategies typically include the use of different, stronger antibiotics; however, new [[strain (biology)|strains]] of MRSA have recently emerged that are resistant even to these drugs.<ref name=Schito_2006>{{cite journal |last=Schito |first=Gian C. |date=March 2006 |title=The importance of the development of antibiotic resistance in ''Staphylococcus aureus'' |journal=Clinical Microbiology and Infection |volume=12 |issue=Suppl s1 |pages=3–8 |pmid=16445718 |doi=10.1111/j.1469-0691.2006.01343.x|doi-access=free }}</ref> This is an [[evolutionary arms race]], in which bacteria develop strains less susceptible to antibiotics, while medical researchers attempt to develop new antibiotics that can kill them. A similar situation occurs with [[pesticide resistance]] in plants and insects. Arms races are not necessarily induced by man; a well-documented example involves the spread of a gene in the butterfly ''[[Hypolimnas bolina]]'' suppressing male-killing activity by ''[[Wolbachia]]'' bacteria parasites on the island of [[Samoa]], where the spread of the gene is known to have occurred over a period of just five years.<ref>{{cite journal |last1=Charlat |first1=Sylvain |last2=Hornett |first2=Emily A. |last3=Fullard |first3=James H. |last4=Davies |first4=Neil |last5=Roderick |first5=George K. |last6=Wedell |first6=Nina |last7=Hurst |first7=Gregory D.D. |display-authors=3 |date=13 July 2007 |title=Extraordinary Flux in Sex Ratio |journal=[[Science (journal)|Science]] |volume=317 |issue=5835 |page=214 |doi=10.1126/science.1143369 |pmid=17626876|bibcode=2007Sci...317..214C |s2cid=45723069 }}</ref><ref>{{cite journal |last1=Moran |first1=Gregory J. |display-authors=etal |title=Methicillin-Resistant S. Aureus Infections among Patients in the Emergency Department |journal=New England Journal of Medicine |date=2006 |volume=355 |issue=7 |pages=666–674 |doi=10.1056/NEJMoa055356 |pmid=16914702 |doi-access=free }}</ref>

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