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PERSPECTIVES

manipulate genetic materials. Genetic trans-formation, also called genetic engineering, isone kind of biotechnology.)

Why were similar concerns not expressed70 years ago when maize hybrids were bredand released rapidly and on a large scale in theheart of the United States ‘Corn Belt’? I willconsider these questions in the light of thefollowing account of the origins and develop-ment of hybrid maize.

Darwin, maize and hybrid vigourCharles Darwin did many experiments totest his theory on the origin of species3. Oneof them involved a comparison of inbred andcross-pollinated maize. He noted that theprogeny of cross-pollinated maize plantswere 25% taller than the progeny of self-pol-linated plants and had greater tolerance tocooler growing conditions. From theseexperiments, he concluded in 1876 that, as ageneral rule, cross-pollinated (hybrid) plantshave “greater height, weight, and fertility”ascompared with their self-pollinated counter-parts because of their “greater innate consti-tutional vigour”4.

In the United States, William Beal atMichigan State College was encouraged byDarwin’s observations on hybrid vigour andhybridized pairs of open-pollinated varietiesof maize. Beal observed increased vigour andgrain yield in the hybrids of different varietiesand, in 1880, he encouraged the use of thismethod5–7. However, because the results offurther experiments were unpredictable5,hybridization seemed to have no future as away to improve maize yields and general per-

formance. But other methods were in theprocess of development.

New breeding methodsImproved varieties. Around the turn of thetwentieth century, farmers in the UnitedStates began to look harder than before forways to increase maize yields. Urban popula-tions were increasing rapidly with a con-comitant increase in the demand for meat,which in turn increased demand for feedgrains. As new lands were no longer avail-able for exploitation, increased productionneeded to come from higher yields. The useof plant breeding to produce new and/orimproved, higher-yielding varieties of maizelooked like a promising option. Those farm-ers and scientists who selected new breedingvarieties rose to the challenge.

Disappointingly, the use of ‘improvedvarieties’ did not produce substantialincreases in yield. Average maize yields inthe midwestern Corn Belt state of Iowa,for example, were essentially unchangedduring the first three decades of the twentieth century8.

With hindsight, we know that the primaryreason for lack of success in variety improve-ment by either farmers or scientists was thattheir selection methods were not very power-ful, as judged by modern standards of statisti-cal design and genetic theory9.

Inbred-hybrid method. Meanwhile, twoyoung scientists laid the foundations for anew method of maize breeding5,10. GeorgeHarrison Shull and Edward Murray East,working well away from the midwesternCorn Belt at two separate institutions on theAtlantic seaboard (East worked inConnecticut, Shull on Long Island in NewYork.), independently rediscovered the phe-nomenon of inbreeding depression andhybrid vigour in maize, and reported theirresults independently in 1908 (REFS. 11,12).They went further than Darwin did, by self-pollinating several generations to produceessentially homozygous (pure-breeding)

Hybrid maize was one of the first examples ofgenetic theory successfully applied to foodproduction. When first introduced, it seemedalmost miraculous; sturdy hybrids convincedsceptical farmers that ‘the professors’ andtheir arcane science could do them somegood. Strangely, the genetic basis of heterosis(hybrid vigour) was and still is unknown. But tothis day, newer hybrids continue to outyieldtheir predecessors; they do so because theyare tougher and healthier.

Hybrid maize (Zea mays) is not new, but thebiological and sociological bases on which itwas built are now considered as new — anddisturbing — by some segments of the public.

When hybrid maize was invented andpresented to US farmers in the first decadesof the twentieth century, it was based ontwo new operations, one biological and theother socio-economic. First, strange manip-ulations (forced inbreeding and controlledhybridization) produced biological prod-ucts that had never before existed in nature.Second, farmers gave up their time-hon-oured practice of saving their own varietiesof seed in favour of annual purchases ofhybrid maize seed.

These two actions are deplored today bysome elements of society as the undesired andpotentially dangerous consequences of theapplication of biotechnology (especially, ofgenetic transformation) to plant breeding1,2.(The term ‘biotechnology’has many defini-tions, but is used here to refer to the branch ofmolecular biology that uses recombinantDNA technology to study, categorize and

NATURE REVIEWS | GENETICS VOLUME 2 | JANUARY 2001 | 6 9

Biotechnology in the 1930s:the development of hybrid maizeDonald N. Duvick

T I M E L I N E

© 2001 Macmillan Magazines Ltd

7 0 | JANUARY 2001 | VOLUME 2 www.nature.com/reviews/genetics

P E R S P E C T I V E S

the United States Department of Agriculture(USDA), agricultural colleges and (a few) pri-vate companies. Despite their diversity, theywere united in their belief that the inbred-hybrid method would succeed where otherbreeding methods had failed.Their confidencewas based on two premises: first, that hybridvigour gives extra yield;and second, that indi-vidual hybrids can be precisely reproducedyear after year. The hybrids can be preciselyreproduced because they are crosses of uni-form inbred lines that, in turn, can be preciselyreproduced by self-pollination.

The technique was simple: develop inbredlines, find their best combination in hybridsby running replicated yield trials of the dif-ferent combinations, produce the seed ofselected hybrids and deliver it to farmers.

In reality, there were several complica-tions, but the basic method was so simplethat, in the early years, anyone with energy,time and ability could learn to apply it. Oneother item was not exactly a problem butrather a mystery. No one knew the geneticbasis for heterosis — hybrid vigour. If thiswere known, breeding could be more pre-cise and hybrid yields presumably could beadvanced further than by using ‘cut and try’(empirical) methods. To this end, theorieswere proposed and experiments conducted

The inbred-hybrid idea did not die, how-ever. A few years after the 1908 announce-ments, one of East’s students, Donald F.Jones in Connecticut, came up with a solu-tion to the problem of seed cost13. ‘Doublecross hybrids’ could be made, by crossingtwo ‘single cross hybrids’. (A single cross is across of two inbred lines; see BOX 1.) Thedouble cross, although perhaps lower yield-ing than the best single crosses, nevertheless,would be much better than the best open-pollinated varieties. Seed production onhigh-yielding single cross parents wouldbring seed prices down to a level that farm-ers could afford. This news, published in1918, electrified a small group of scientistsand maize-breeding enthusiasts.

The public and private sectorsEven before Jones’announcement of the dou-ble cross method, several young scientists thatwere working in the public sector had begunto inbreed maize, with no knowledge of theprecise method that would be followed tomake hybrids.After Jones’announcement, theinitial group was joined by a few moreresearchers, raising their total to about onedozen.This diverse group included agricultur-al scientists, a farmer and a magazine editor.They worked at several institutions, such as

inbred lines that were then crossed to producehybrids. Shull coined the term “heterosis” todescribe hybrid vigour.

Both men recognized the potential of the‘inbred-hybrid method’for producing high-yielding maize hybrids that, once identified,could be reproduced without change year afteryear. Hybrid seed could be made on a large,farm-field scale (as opposed to labour-inten-sive hand pollination) by removing the tassels(detasselling) from one inbred and allowing itto be pollinated by a second inbred planted inadjacent blocks (FIG.1).Maize is unique amongthe cereal crops in that male and female flowersare borne on separate organs — tassel and earshoot, respectively — and it is wind-pollinated.No other crop is so well suited by nature tolarge-scale hybridization.

But neither East nor Shull believed thatfarmers could grow hybrids profitably. Theinbreds developed by Shull and East were soweak and low yielding that seed yields werevery low or absent (BOX 1). Seed productioncosts — and therefore seed prices — would betoo high; the extra expense for annually pur-chased seed would be greater than the value ofthe extra yield of the hybrid.And freshly madehybrid seed was needed each season, for yieldsdropped precipitously (15% or more) if seedsaved from the hybrid plants was replanted.

Box 1 | How to make a double cross hybrid

To make a double cross hybrid, four inbreds are crossed pairwise, making twosingle crosses: B ×A and C × D. The two single crosses are crossed, giving a doublecross: (B ×A) × (C × D). Hybridization is effected on a field scale by plantingalternating blocks of the two lines to be crossed (such as inbreds A and B), thendetasselling one block (such as inbred B). Inbred B therefore is pollinatedexclusively by inbred A, and all seed on inbred B is hybrid, B ×A.

Breeding by farmers produced several popular open-pollinated varieties, suchas Reid’s Yellow Dent and Krug’s Yellow Dent. Mr. Reid started with a mixture ofa New England Flint variety (too early) and a Southern Dent variety (too late)and developed a high-yielding variety of the right maturity for central Illinois.Further gains were more difficult. Modern geneticists say that neither thebreeding protocols used by farmers or the earliest scientific breeding programmeswere designed to give sharp and continuing increases in performance.Experiments were not replicated a sufficient number of times, and there was toolittle control over the source of the pollen used to fertilize the selected ears.Breeding designs based on current genetic theory enable breeders to improveopen-pollinated varieties at about the same rate as that achieved by breeders ofhybrid maize, but this knowledge was not available in the nineteenth and earlytwentieth centuries. It is now thought that, even using modern designs, the besthybrids will always outdo the best open-pollinated varieties. Open-pollinatedvarieties are a diverse collection of hybrid plants and the performance of a varietyis equal to the average of all of its plants, from best to worst. Therefore the besthybrid, developed and dependably reproduced with the inbred-hybrid breedingmethod, will always be superior to the best open-pollinated variety, even thoughit may not be superior to the very best plants in that variety.

This illustration, from a farm magazine in the 1930s, shows how to make seed of a double cross maize hybrid. Note the difference in size between inbred andhybrid ears. Education and advertising were combined then, as they are now. Image courtesy of Pioneer Hi-Bred International, Inc.



Hybrid maize. Within ten years of Jones’proclamation, the first breeders were produc-ing successful hybrids. Beginning in the early1930s, interest in, and demand for, hybridmaize rose steadily among farmers in theUnited States16 (FIG. 2a). Maize breeders havecontinually turned out higher-yieldinghybrids, year after year17–19 (FIG. 2b), and farm-ers have adopted them after cautious trials ontheir own farms. In 1997, United States maizeyields averaged 8 tons hectare–1, comparedwith 1 ton hectare–1 in 1930 (REF.20).

Hybrids were not entirely responsible foradvances in maize yields, however. Startingaround the 1950s, the increasingly widespreaduse of synthetic nitrogen fertilizers, chemicalweed killers, and more efficient planting andharvesting machinery also contributed tohigher yields17–19,21.

Surprisingly, improvements in heterosishave not contributed to higher yields.Experiments have shown that heterosis(calculated as the difference in yieldbetween a single cross hybrid and the meanof its two inbred parents) is unchangedover the years. The yields of the inbred lineshave risen at almost the same rate as hybridyields22. It seems that yield gains have comeprimarily from genetic improvements intolerance to stresses of all kinds (such astolerance to disease and insects, denseplanting, drought or low soil fertility). Thenewer hybrids are tougher than their predecessors and shrug off droughts (forexample) that would have damaged the older hybrids and devastated their open-pollinated parents.

but, to this day, there is no completely satis-factory explanation for the phenomenon ofheterosis in maize or in any other species14.Fortunately, a lack of understanding hasnever hindered the use of the phenomenon.

But in the 1920s, these problems were allin the future. The ‘hybrid maize’enthusiastswere occupied primarily with findinginbreds that made outstanding hybrids. Aswith many interest groups, the ‘hybridmaize breeders’came to know each otherand developed an informal exchange ofinformation and materials. They neededeach other’s inbreds, for no one had enoughof them to make a series of good double-cross hybrids.

In the 1920s (and for some decadesthereafter), the primary source of ideas, the-ories and germ plasm was the public-sectormaize breeders at the agricultural collegesand in the USDA. They published their find-ings in the scientific literature and, impor-tantly, furnished breeding materials, such asinbred lines, to all that asked. The public sec-tor through the extension services (depart-ments through which farmers’and scientistsexchange information) of its agriculturalcolleges, also effectively educated the farm-ing community (and the interested non-farming public) about the advantages ofhybrid maize.

Without the contributions from the public sector, the commercial maize breed-ers probably could not have succeeded in the early years, for individually they simplydid not have enough inbred lines orenough knowledge about how best to makeand test hybrids15.


Figure 1 | Detasselling maize plants Detasselling — pulling tassels — is vital for the production ofhybrid maize. The detasselled plants are called ‘females’; they will bear the hybrid seed. In the earlyyears, men on foot did the detasselling, as in this photo from the 1930s. In later years, high schoolboys and girls were recruited to do the job, also on foot. Today, youths are still the chief laboursource, but they usually ride in special motorized carriers, thereby increasing the speed andprecision of their work. (Image courtesy of Pioneer Hi-Bred International, Inc.)

01930 1935 1940 1945

Year1950 1955 1960

20

40

60

80

100a

b

51930

= Iowa= USA

1940 1950 1960Year of hybrid introduction

1970 1980 1990

6

7

8

9

10

11

Figure 2 | Maize hybrids: area planted andyield potentials. a | Per cent of maize areaplanted to hybrids, from 1930 to 1960, in Iowa(red) and in the United States (green). During the1930s, hybrids almost completely replaced open-pollinated varieties in most of the Corn Belt and,by 1960, virtually all maize plantings in the UnitedStates were hybrid. Yield gains paralleledincreases in area planted to hybrids. Iowa maizeyields advanced on average from 2 tons hectare–1

in 1930 to 5 tons hectare–1 in 1960; United Statesmaize yields advanced from 1 ton hectare–1 in1930 to 4 tons hectare–1 in 1960. (Adapted fromREF. 20.) b | Grain yields (in tons hectare–1) of 36popular hybrids introduced in central Iowa from1934 to 1991, according to tests conducted incentral Iowa in 1991–1994. New maize hybridsyield more than their predecessors, and are alsocontinually being improved for other traits, suchas disease resistance and tolerance to drought.Researchers have concluded that, on average,improvements in hybrids have been responsiblefor about 50–70% of the on-farm yield gains sincetheir introduction, and changes in agronomicpractices (such as more fertilizer and better weedcontrol) have been responsible for the remainder.(Adapted from REF. 18.)




tus as independent seed savers, and eventhough hybrids as such were looked on asstrange new creations of science. Havingtraced the development of hybrid maize, theseand related questions can be addressed.

Farmers gave up their status as indepen-dent seed savers because they found by expe-rience that they would profit more by doingso. They were already giving up their status asindependent power suppliers on their farms,for example, as they moved from horse powerto tractor power and from hand harvest tomechanical maize pickers.

Although farmers viewed hybrids as newand strange creations of science, they saw noadverse effects on either their crops or theirlivestock. It is true that, in the early days,some farmers feared that the abnormallyhigh yields from hybrids would drain the soilof needed fertilizer elements. And there werecomplaints about some of the first hybrids,to the effect that the kernels were too flintyand hard for cows to chew. Seed companiesbred new hybrids to satisfy the second com-plaint, and the first concern turned out to bewithout foundation if normal soil fertilitypractices were used.

The farmers’primary fear was not that sci-ence might create unmanageable ‘monsters’(today’s widespread point of view), but thatscientists claimed more power to help agricul-ture than they really possessed.

Public and private breeders. In the early yearsof the hybrid era, people were undecidedabout how to deliver hybrids to the farmer.Farmers had the option to produce them ontheir own farm using single cross parent seedpurchased from the agricultural colleges, or topurchase ‘ready to plant’hybrid seed fromfarmer cooperatives or from commercial seedcompanies (FIG. 3).All methods were tried, butin the end the seed companies turned out tobe the farmers’choice.

Once the advantages of hybrids (and thefact that farmers would buy them) were shown,seed companies sprang up across the country,especially in the Corn Belt states15 (FIG. 4).Starting with four pioneering companies, thenumbers grew exponentially in the 1930s. By1995, 305 independent companies wereinvolved with the production and sale of hybridmaize seed. As with most industries, a smallnumber of large companies dominated thebusiness, accounting for perhaps 70% of thesales.Despite their small market share, the smallcompanies have an important role in the indus-try.They provide an alternative to farmers whodo not want to buy from the larger companies.

The exchange of information and breed-ing materials among private- and public-sec-tor breeders changed as the seed industrymatured. Almost from the beginning, seedcompanies kept the pedigrees of their hybridssecret and they soon stopped trading theirinbred lines. By about the mid-1930s, allexchange of inbreds and other advancedbreeding materials was one-way, from thepublic to the private sector.

The roles of the public- and private-sectorbreeders also changed. The large companieswith strong breeding programmes hadincreasingly less need for inbreds developed bythe public sector, although the smaller compa-nies still depended on them. Over time,‘foun-dation seed companies’were formed expresslyto breed inbred lines for lease to the small seedcompanies, thereby filling the role of the pub-lic-sector breeders.The public-sector breedersin turn shifted their primary emphasis fromthe development of inbreds and hybrids tostudying the theoretical basis for producingimproved inbreds and hybrids, as well as otherneeded aspects of maize-breeding research.

The relationship between public and pri-vate sector breeders still remains close; theyhave mutually supportive roles in the nation’smaize breeding programme.

Consequences of hybrid maizeAcceptance. In the opening paragraphs of thisarticle I asked why the maize hybrids wereaccepted without public outcry in the 1930s,even though farmers had to give up their sta-

An important change in hybrid seedproduction and performance was, in asense, a byproduct of the increases ininbred yield. By the 1960s, the newestinbreds were so high-yielding that itbecame practical to use them as seed par-ents, and so to produce single cross hybridsfor sale. The best single crosses alwaysyielded more than the best double crossesbut, as noted earlier, commercial produc-tion of single cross hybrids was not feasiblein the first decades of hybrid maize breed-ing because of the low yield potential ofinbreds from that era.

Figure 3 | The introduction of hybrid maizeseeds. The ‘seed corn companies’ effectively andenergetically introduced hybrid maize to cautiousfarmers. They recruited well-known andrespected farmers as part-time salesmen,working on commission. They gave smallamounts of free seed of new hybrids to farmersand encouraged the prospective customers tocompare them with their present varieties on theirown farms and using their own farming methods.The salesman and/or his supervisor often wouldhelp the farmer harvest the comparison. In theprocess, the sales people learned about thefarmers’ needs and desires in maize hybrids,which they passed on to the breeders. So, therelationship between farmers and seedcompanies from the beginning was almost on aneighbour to neighbour basis. The relationshipremains much the same today, with modificationsbecause of the changing nature of farming andfarmers (much larger scale, more advancedtechnologically and more business-like). Image courtesy of Pioneer Hi-Bred International, Inc.

Figure 4 | Maize quality control in the earlyyears. The fledgling seed companies devised a‘sorting belt’, allowing inspectors to examineevery ear before shelling. They wanted to be surethe seed ears were free of damage from diseaseor insects, and of the right type. Women replacedmen in many of the seed production operationsduring the Second World War, when young menwere in the armed services. Image courtesy of Pioneer Hi-Bred International, Inc.



have enlarged their operations (helped alsoby the adaptation of maize hybrids to mech-anization) and so farm numbers havedecreased. Maize production on the whole ismore efficient, but some farmers in particu-lar have suffered.

Future prospectsHybrid maize now has spread over all com-mercial maize growing regions of the indus-trialized countries such as North America andEurope, and also the industrial agriculturesections of developing countries such asArgentina, China and Brazil.

The story of the development of hybridmaize in Europe may be instructive. As theEuropean economy improved after theSecond World War, meat became more popu-lar and this increased the demand for feedgrains, including maize. American maizehybrids were not adapted to the European cli-mate, except in the south. European breedersdeveloped inbreds from early European flintvarieties. The flint inbreds, hybridized toUnited States inbreds, gave high yieldinghybrids with adaptation to the cool growingseason of northern Europe. Hybrid maize isnow an important crop in all continentalEuropean countries south of the Baltic, wher-ever commercial grain farming is important.

Biotechnology (including genetic transfor-mation) is in the future of hybrid maizebreeding everywhere in the world, but when itwill achieve widespread use is uncertain. Theexpense of applying biotechnology is highand it will be difficult for seed companies tomake a profit without raising seed prices ontransgenic hybrids. But farmers will buy suchhigher priced hybrids only if they believe theywill more than recoup their extra investmentin seed. Additionally, a powerful campaignagainst GMOs (genetically modified organ-isms) intends to block use of transgenics inboth animal and crop agriculture (especiallyaiming at agribusiness). The outcome of thiscampaign will notably affect, possibly in anegative fashion, the direction and utility ofthe quintessential commercial seed breedingactivity, hybrid maize.

But the fundamental knowledge thataccrues from research in molecular biology ofplants is scientifically so empowering that Icannot imagine a future in which biotechnol-ogy will not be beneficially applied to maizebreeding (or any other biological manipula-tion). It will be applied, however, with moredelay and more difficulty than imagined twodecades ago by its proponents.

Donald N. Duvick is at 6837 Northwest BeaverDrive, P.O. Box 446 Johnston, Iowa 50131, USA.

e-mail: [email protected]

There was no concern whatsoever aboutthe adverse effects of hybrid maize onhuman health or ecosystems. In the 1930s(the decade of ‘The Great Depression’), theoverriding public concern was to haveample and affordable supplies of food,clothing and shelter.

An important difference between thenand now is that hybrids of the 1930s weremade by genetic manipulations that used‘natural methods’of gene transfer (pollen tostigma), whereas today’s transgenic crop vari-eties require ‘unnatural’laboratory manipula-tions. (Gene transfer across very wide taxo-nomic distances does occur in nature but notthrough gene guns or tissue culture, and theproducts are not multiplied and distributedso widely and rapidly as transgenic farmcrops.). Although the operations and prod-ucts of hybrid maize breeding were thoughtof as ‘unnatural’(or at the least, highly unusu-al) in the 1930s, they are no longer consideredas such; they are thought of as an applicationof a natural phenomenon.

Perhaps the most important difference isthat, in the 1930s, there were no social/envi-ronmental organizations conducting pow-erful campaigns to educate the non-farmingpublic sector about the possible dangers (tohealth, the environment or society) of grow-ing or eating crop varieties created with‘unnatural’ techniques (for example, REFS1,23,24). In the 1930s, to convince farmers ofthe utility and safety of these new creations— hybrids — was sufficient to ensure theiracceptance by all. Today, one primarily mustconvince the non-farming public of thesafety of the new creations of genetic engi-neering. The farmers’opinion also counts,but only secondarily.

A final difference is that, contrary to the1930s, today’s scientific establishment has nottaken the lead to introduce and explaintransgenic crop varieties to the public andoften is divided in its opinions on this sub-ject, as well as on the general topic of biotech-nology in plant breeding. The scientists arenot alone in this regard; the entire questionof biotechnology and its applications is com-plicated and controversial for reasons that gowell beyond science. As one commentatorhas stated25,“the larger biotechnology debate… is riddled with ideological, ethical, andother normative evaluations… [As] historykeeps teaching us, ideology and world viewwill not easily be influenced by the results ofscientific research”.

One can speculate that use of hybridmaize might have been hindered or evenblocked, if today’s socio-economic, foodand environmental concerns and today’s

healthy economy had prevailed in theUnited States in the 1930s, concurrent withthe 1930s state of knowledge about geneticmanipulation. But perhaps it is not realis-tic to expect that today’s environmentaland food quality concerns could existwithout support from today’s advancedbiological knowledge.

Effects. Despite the enthusiastic acceptanceof hybrid maize by American farmers (andindirectly by the non-farming public) it willbe beneficial to look briefly at the effects(favourable or otherwise) of hybrid maize,biologically, economically and sociologically,during the past 70 years.

Genetic diversity of maize on the farm hasbeen reduced, primarily because hybrids aremore genetically uniform than open-polli-nated varieties. Genetic diversity providesprotection against unexpected kinds ofweather, disease and insect pests.

However, genetic diversity on the farm isonly one kind of diversity26. Breeders workfrom a large pool of genetic diversity in thehighly diverse ‘breeding pools’from whichthey extract inbred lines. They also can ‘crossin’breeding materials from anywhere in theworld, giving them opportunity to add analmost uncountable number of new traits asthey are needed. Hybrids therefore increas-ingly have more built-in genetic diversity andtheir genetic components change every year,as new hybrids replace outdated older ones. Itseems fair to say that, in a given season, indi-vidual farmers work with less diversity but,over the years, they have access to more diver-sity than in pre-hybrid days.

Today’s hybrids are more tolerant to stressthan were the open-pollinated varieties of the1920s and earlier27,28. However, the hybrids’increased robustness has encouraged farmersto apply heavier amounts of fertilizer (espe-cially nitrogen), because the hybrids can takeadvantage of the increased nutrient supplieswithout suffering from the stress of morerapid growth and higher productivity. Soindirectly, hybrids (along with all moderncereal varieties) have contributed to groundwater pollution.

Mechanization of maize growing (in par-ticular of harvesting machinery) has beenencouraged by use of hybrids because theydo not lodge (fall over) as much as open-pol-linated varieties. These hybrids are moreamenable to machine harvest, and so haveaided the trend towards larger farms andfewer farmers.

The heightened yields of hybrids havebenefited farmers economically, in particu-lar the most efficient ones. They, in turn,





cal and legal issues that arise from humanES cell research, and how public policyshould accommodate them.

Legality of human embryo researchLegal treatment of the use of human fetaltissue or the destruction of human embryosto obtain ES cells for research varies widelythroughout the world. The United States,the United Kingdom and many other coun-tries permit the use of human fetal tissuefor research when a woman’s decision todonate fetal tissue is clearly separate fromthe decision to abort. Although mostAmerican states permit ES cell research thatrequires the destruction of human embryos,federal law prohibits the direct funding ofembryo destruction to obtain such cells4,5.However, federal law permits the funding ofresearch on human embryonic tissue thathas been derived with private funds, provid-ed that guidelines for how these cells shouldbe derived have been followed6. Althoughthe United Kingdom at present only per-mits human embryos to be used to studyinfertility, contraception and birth defects,an expert group at the Department ofHealth has recommended that embryoresearch involving cell-based treatments beadded to the list of acceptable purposes7.Germany and France prohibit destructiveembryo research, whereas other EuropeanUnion members are split on the question8,9.Australia also has a mixture of positions,with the state of Victoria specifically ban-ning “destructive embryo research” thatproduces ES cells for research10, whereas thestates of New South Wales and Queenslandpermit it according to the guidelines of theAustralian Medical Research Council11.

A legal ban on destroying humanembryos to produce ES cells, however, doesnot mean that research on ES cells legallyderived in another jurisdiction is also prohib-ited. The United States Congress’ban on fed-eral funding of human embryo researchrestricts only federal support for the deriva-tion of human ES cells. The ban does notaffect research on human ES cells that havebeen derived by using private funds, provid-ed that National Institutes of Health (NIH)regulations for how those cells were derivedhave been observed6. Similarly, human ES cellresearch is now occurring in Victoria, despiteits ban on embryo destruction, with cellsderived in Singapore where their destructivederivation is legal.

Some countries or states, includingMichigan in the United States12 and Victoriain Australia, now ban human cloning with-out drawing a distinction between cloning

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17. Russell, W. A. Genetic improvement of maize yields.Advances in Agronomy 46, 245–298 (1991).

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21. Cardwell, V. B. Fifty years of Minnesota corn production:sources of yield increase. Agronomy J. 74, 984–990(1982).

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23. Turning Point Project. Biotechnology = Hunger (PaidAdvertisement by Turning Point Project on behalf of 22non-governmental organizations). The New York Times A5(New York, 8 November, 1999).

24. Goldburg, R., Rissler, J., Shand, H. & Hassebrook, C.Biotechnology’s Bitter Harvest —Herbicide Tolerant Cropsand the Threat to Sustainable Agriculture (TheBiotechnology Working Group/The TidesFoundation/Environmental Defense Fund, New York, NewYork, 1990).

25. van Dommelen, A. Hazard Identification of AgriculturalBiotechnology: Finding Relevant Questions (InternationalBooks, Utrecht, the Netherlands, 1999).

26. Duvick, D. N. Genetic diversity in major farm crops on thefarm and in reserve. Economic Botany 38, 161–178 (1984).

27. Duvick, D. N. in Developing Drought- and Low N-TolerantMaize Proceedings of a Symposium, March 25-29, 1996,CIMMYT, El Batan, Mexico. (eds Edmeades, G. O.,Bänziger, M., Mickelson, H. R. & Peña-Valdivia, C. B.)332–335 (CIMMYT, México, D. F., 1997).

28. Tollenaar, M., McCullough, D. E. & Dwyer, L. M. in GeneticImprovement of Field Crops (ed. Slafer, G. A.) 183–236(Marcel Dekker, Inc., New York-Basel-Hong Kong, 1994).

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The use of human embryonic stem cells to replace damaged cells and tissues promises future hope for thetreatment of many diseases. However,many countries now face complex ethical and legal questions as a result of the research needed to develop these cell-replacement therapies. The challenge that must be met is how to permit research on human embryonictissue to occur while maintaining respectfor human life generally.

Embryonic stem (ES) cell research offers thehope of cell-replacement therapy for dis-eases such as Parkinson disease, diabetesand cardiac myopathy, but formidable sci-entific and clinical challenges must be over-

come before such therapies could becomeavailable1,2. For example, scientists need tolearn how to direct pluripotent ES cells todifferentiate into the required cell or tissuetype3. Clinicians must then determine thetransplanted cells’ immune compatibilitywith the host, and where, and in whatamounts, to replace cells in diseased organsto achieve a therapeutic effect. These scien-tific efforts are also complicated by ethicalconcerns about obtaining human ES cellsfrom aborted fetuses or from the destruc-tion of early human embryos. The resultingcontroversy has delayed or stopped humanES cell research in some countries, andcould affect the extent to which human ES-cell derived therapies are developed andused. This article will survey the main ethi-

Human embryonic stem cell research:ethical and legal issuesJohn A. Robertson

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