Editing Twin study (section)

== History ==
[[File:Gustav III by Alexander Roslin - torso (Nationalmuseum, 15330).png|thumb|221x221px|[[Gustav III]] of [[Sweden]] was the first to use identical twins in a comparative study of medical outcomes. ]]
[[Twins]] have been of interest to scholars since early civilization, including the early physician [[Hippocrates]] (5th century BCE), who attributed different diseases in twins to different material circumstances,<ref>{{Cite book |url=https://archive.org/details/hippocratesinwor00owse |url-access=registration |title=Hippocrates in a World of Pagans and Christians |last=Temkin |first=Owsei |date=1991 |publisher=JHU Press |isbn=9780801840906 |pages=[https://archive.org/details/hippocratesinwor00owse/page/132 132] |language=en}}</ref> and the stoic philosopher [[Posidonius]] (1st century BCE), who attributed such similarities to shared astrological circumstances.<ref>Cicero, De Divinatione, (On Divination), ii. 42</ref> 

[[Gustav III]], King of [[Sweden]] was the first to [[Gustav III of Sweden's coffee experiment|commission]] a medical study using identical twins.{{Cn|date=July 2023}}{{Original research inline|date=July 2023}} Gustav's father, [[Adolf Frederick of Sweden|Adolph Frederick]] had been an opponent of stimulating drinks such as [[tea]] and [[coffee]], signing the ''Misuse and Excesses Tea and Coffee Drinking Edict'' in 1757.<ref>{{Cite journal |last=Afshari |first=Reza |date=2017 |title=Gustav III's risk assessment on coffee consumption; A medical history report |journal=Avicenna Journal of Phytomedicine |volume=7 |issue=2 |pages=99–100 |issn=2228-7930 |pmc=5355814 |pmid=28348964}}</ref> Both Gustav III and his father had read and been strongly influenced by a 1715 treatise from a [[French people|French]] physician on the dangers of what would later be identified as [[caffeine]] in tea and coffee.<ref>{{Cite web |title=Linné on line – Coffee – rat poison or miracle medicine? |url=http://www2.linnaeus.uu.se/online/pharm/kaffete.html |access-date=2022-10-04 |website=www2.linnaeus.uu.se}}</ref> After assuming the throne in 1771 the king became strongly motivated to demonstrate to his subjects that coffee and tea had deleterious effects on human health. To this end he offered to commute the death sentences of a pair of twin murderers if they participated in a primitive [[clinical trial]]. 

Both condemned men agreed and subsequently spent the rest of their lives in prison fulfilling the king's demands: that one twin drink three pots of coffee every day and the other three pots of tea. The tea drinking twin died first at the age of 83, long after Gustav III, who was [[Gustav III of Sweden#Assassination|assassinated in 1792]]. The age of the coffee-drinking twin at his death is unknown, as both doctors assigned by the king to monitor this study predeceased him. The ban on coffee and tea in Sweden was lifted in 1823.<ref>{{Cite journal |last=Afshari |first=Reza |date=2017 |title=Gustav III's risk assessment on coffee consumption; A medical history report |journal=Avicenna Journal of Phytomedicine |volume=7 |issue=2 |pages=99–100 |issn=2228-7930 |pmc=5355814 |pmid=28348964}}</ref><ref>{{Cite journal |last1=Knutsson |first1=Anna |last2=Hodacs |first2=Hanna |date=2021-11-18 |title=When coffee was banned: strategies of labour and leisure among Stockholm's poor women, 1794–1796 and 1799–1802 |journal=Scandinavian Economic History Review |volume=71 |issue=2 |pages=176–198 |doi=10.1080/03585522.2021.2000489 |s2cid=244415520 |issn=0358-5522|doi-access=free }}</ref>

A more recent study is from [[Galton|Sir Francis Galton's]] pioneering use of twins to study the role of genes and environment on [[Human development (biology)|human development]] and behavior. Galton, however, was unaware of the difference between [[monozygotic|identical]] and [[dizygotic|DZ]] twins.<ref>{{Cite journal | last1 = Rende | first1 = R. D.| last2 = Plomin | first2 = R.| last3 = Vandenberg | first3 = S. G.| doi = 10.1007/BF01067795 | title = Who discovered the twin method? | journal = [[Behavior Genetics (journal)|Behavior Genetics]]| volume = 20 | issue = 2 | pages = 277–285 | year = 1990 | pmid =  2191648| s2cid = 22666939}}</ref> This factor was still not understood when the first study using psychological tests was conducted by [[Edward Thorndike]] (1905) using fifty pairs of twins.<ref>{{Cite journal|url=https://www.pdcnet.org/pdc/bvdb.nsf/purchase?openform&fp=jppsm&id=jppsm_1905_0002_0020_0547_0553|title=Measurement of Twins|last=Thorndike|first=Edward L.|date=1905-01-01|journal=The Journal of Philosophy, Psychology and Scientific Methods|volume=2 |issue=20 |pages=547–553 |doi=10.2307/2011451 |jstor=2011451 |access-date=2019-03-11}}</ref><ref>{{Cite book|url=https://play.google.com/books/reader?id=13uo6WCRuvgC|title=Measurements of Twins|last=Thorndike|first=Edward Lee|date=1905|publisher=Science Press|language=en}}</ref> This paper was an early statement of the hypothesis that family effects decline with age. His study compared twin pairs age 9–10 and 13–14 to normal siblings born within a few years of one another.[[File:Francis Galton.jpg|thumb|140px|right|[[Francis Galton]] laid the foundations of [[behavior genetics]] as a branch of [[science]].]]

Thorndike incorrectly reasoned that his data supported for there being one, not two, twin types. This mistake was repeated by [[Ronald Fisher]] (1919), who argued
{{quote|The preponderance of twins of like sex, does indeed become a new problem, because it has been formerly believed to be due to the proportion of identical twins. So far as I am aware, however, no attempt has been made to show that twins are sufficiently alike to be regarded as identical really exist in sufficient numbers to explain the proportion of twins of like sex.<ref>{{Cite journal
| last1 = Fisher | first1 = R. A.
| title = The Genesis of Twins
| journal = Genetics
| volume = 4
| issue = 5
| pages = 489–499
| year = 1919
| doi = 10.1093/genetics/4.5.489
| pmid = 17245935
| pmc = 1200469
}}</ref>}}

An early, and perhaps first, study understanding the distinction is from the [[Germans|German]] geneticist [[Hermann Werner Siemens]] in 1924.<ref>{{cite book | first = Hermann Werner | last = Siemens | year = 1924 | title = Die zwillingspathologie; ihre bedeutung, ihre methodik, ihre bisherigen ergebnisse | publisher = [[Springer Science+Business Media|Springer]] | location = Berlin | oclc = 18362377 }}</ref> Chief among Siemens' innovations was the ''polysymptomatic similarity diagnosis''. This allowed him to account for the oversight that had stumped Fisher, and was a staple in twin research prior to the advent of molecular markers.

[[Wilhelm Weinberg]] and colleagues in 1910 used the identical-DZ distinction to calculate respective rates from the ratios of same- and opposite-sex twins in a maternity population. They partitioned co-variation amongst relatives into genetic and environmental elements, anticipating the later work of [[Ronald Fisher|Fisher]] and [[Sewall Wright|Wright]], including the effect of dominance on similarity of relatives, and beginning the first classic-twin studies.<ref name="crow1999">{{cite journal | first=James F. | last=Crow | author-link=James F. Crow | year=1999 | title=Hardy, Weinberg and language impediments | journal=Genetics | volume=152 | pages=821–825 | pmid=10388804 | issue=3 | doi=10.1093/genetics/152.3.821 | pmc=1460671 }}</ref>

A study conducted by [[Darrick E. Antell|Darrick Antell]] and Eva Taczanowski found that "twins showing the greatest discrepancies in visible aging signs also had the greatest degree of discordance between personal lifestyle choices and habits", and concluded that "the genetic influences on aging may be highly overrated, with lifestyle choices exerting far more important effects on physical aging."<ref>{{cite journal |last1=Antell |first1=Darrick E. |last2=Taczanowski |first2=Eva M. |title=How Environment and Lifestyle Choices Influence the Aging Process |journal=Annals of Plastic Surgery |date=December 1999 |volume=43 |issue=6 |pages=585–8 |doi=10.1097/00000637-199912000-00001 |pmid=10597816 |language=en |issn=0148-7043}}</ref>