一些 10.000 年前, 男人从改变动物的狩猎和采集种子和块茎在野外, 对饲养动物和栽培植物附近他住的地方的地方.
在这个漫长的过程, 人类已经极大地改变了他们原先在自然界中发现的动物和植物. 家养的牛, 羊, 猫, 和狗是众所周知的, 但有时人并不知道，类似的驯化已发生，我们成长为作物许多植物, 如玉米, 小麦, 饭, 和大豆. 千百年来, 人类已经选定，并越过植物，有特色，他们喜欢, 如口感更好或更多收益.
This approach made a huge jump forward when in the 19th century the scientist-monk Gregor Mendel discovered the ‘rules’ by which characteristics were inherited from one generation to the next. Later, scientists discovered that the code for the characteristics of plants, animals and micro-organisms are contained in so called ‘genes’, and that genes consist of genetic material, which we call DNA.
In the early 20th century, plant breeders discovered that mutations in plants do not only occur spontaneously, but can also be induced by exposing plant material to radiation or chemicals.
This has become a widely used technique, and many of the crops we consume every day are obtained with the help of mutations induced by chemicals and radiation.
While cross breeding and induced mutations are and will be extremely important tools of plant breeding, they also have a number of limitations:
- When a gene for a desired trait such as disease resistance is not present in the gene pool of maize for example, then it will not be possible to cross such a gene in from an unrelated species such as wheat;
- For some traits, the genes may be available in the gene pool of, again for example, 玉米, but those genes are not expressed enough to actually result in the desired trait;
- For some species, such as fruit trees, cross breeding may take decades, which is too long if we need traits that help address the increasing impacts of climate change. 例如, it took apple breeders over 50 years to cross resistance against scab, which is a major disease in apple trees that requires many sprays with pesticides per season.
- For other species cross breeding is extremely difficult altogether. Bananas, 例如, are sterile and have no seeds. Bananas are multiplied ‘asexually’, which means that to make new banana plants, parts of an existing plant are used. All the resulting bananas are genetically identical.
- The traditional forms of mutation selection by using radiation or chemicals are highly unpredictable and can cause many unintended changes.
- Cross breeding not only brings the desired genes from plant A to plant B (which is usually an ‘elite’ variety that is well adapted to the local environment) but also the tens of thousands other genes of plant A. This so called ‘linkage drag’ forces plant breeders to start a long process of ‘back crossing’.
To overcome these limitations of cross breeding and induced mutation, scientists developed in the 1970s techniques that made it possible to”
- identify a specific gene responsible for a trait in an organism,
- isolate that gene, 和
- bring it into plant cells through a process called “transformation”
This process we call ‘genetic modification’, or ‘genetic engineering’ (in the early days of this technology, it was also referred to as ‘recombinant DNA techniques’).