![]() | It has been suggested that
Human Chimerism be
merged into this article. (
Discuss) Proposed since May 2024. |
A human chimera is a human with a subset of cells with a distinct genotype than other cells, that is, having genetic chimerism. In contrast, an individual where each cell contains genetic material from a human and an animal is called a human–animal hybrid, while an organism that contains a mixture of human and non-human cells would be a human-animal chimera. [1]
Some consider mosaicism to be a form of chimerism, [2] while others consider them to be distinct. [3] [4] [5]
Mosaicism involves a mutation of the genetic material in a cell, giving rise to a subset of cells that are different from the rest.
Natural chimerism is the fusion of more than one fertilized zygote in the early stages of prenatal development. It is much rarer than mosaicism. [5]
In artificial chimerism, an individual has one cell lineage that was inherited genetically at the time of the formation of the human embryo and the other that was introduced through a procedure, including organ transplantation or blood transfusion. [6] Specific types of transplants that could induce this condition include bone marrow transplants and organ transplants, as the recipient's body essentially works to permanently incorporate the new blood stem cells into it.
Natural chimerism has been documented in humans in several instances.
Human-animal chimeras include humans having undergone non-human to human xenotransplantation, which is the transplantation of living cells, tissues or organs from one species to another. [17] [18]
Patient derived xenografts are created by xenotransplantation of human tumor cells into immunocompromised mice, and is a research technique frequently used in pre-clinical oncology research. [19]
Non-artificial chimerism has traditionally been considered to be rare due the low amount of reported cases in medical literature. [27] However, this may be due to the fact that humans might not often be aware of this condition to begin with. There are usually no signs or symptoms for chimerism other than a few physical symptoms such as hyper-pigmentation, hypo-pigmentation, Blaschko's lines, body asymmetry or heterochromia iridum (possessing two different colored eyes). [28] However, these signs do not necessarily mean an individual is a chimera and should only be seen as possible symptoms. Again, forensic investigation or curiosity over an unexpected maternity/paternity DNA test result usually leads to the accidental discovery of this condition. By simply undergoing a DNA test, which usually consists of either a swift cheek swab or a blood test, the discovery of the once unknown second genome is made, therefore identifying that individual as a chimera. [29]
The concept of a "human hermaphrodite" resulting from chimerism is largely a misconception. [30] Most intersex individuals are not chimeras, [31] [30] and most human chimeras are not observed to have intersex traits. [30] Theoretically, if a gynandromorphic human chimera were to have fully functioning male and female gonad tissue, such an individual could self-fertilize; [32] [33] this hypothesis is backed by the fact that hermaphroditic animal species commonly reproduce in this way, and it has been observed in a rabbit. [34] However, no such case of functional self-fertilization has ever been documented in humans; [35] and it is non-existent or extremely rare in mammals, [36] [37] [38] [39] [40] especially in humans. [41] [42] [43] [44] While humans are known to have sex characteristics that diverge from typical males or typical females, these individuals fall under the social umbrella of intersex conditions and traits, and some consider the term "hermaphrodite" to be a slur when applied to them. [45] [46] [47]
On 11 July 2005, a bill known as The Human Chimera Prohibition Act was introduced into the United States Congress by Senator Samuel Brownback; however, it died in Congress sometime in the next year. The bill was introduced based on findings that science has progressed to the point where human and nonhuman species can be merged to create new forms of life. Because of this, ethical issues may arise as the line blurs between humans and other animals, and according to the bill with this blurring of lines comes a show of disrespect for human dignity. The final claim brought up in The Human Chimera Prohibition Act was that there is an increasing amount of zoonotic diseases. With that being said, the creation of human-animal chimeras can allow these diseases to reach humans. [48]
On 22 August 2016, another bill, The Human-Animal Chimera Prohibition Act of 2016, was introduced to the United States House of Representatives by Christopher H. Smith. It identifies a human-animal chimera as:
The bill prohibits the attempts to create a human-animal chimera, the transfer or attempt to transfer a human embryo into a nonhuman womb, the transfer or attempt to transfer a nonhuman embryo into a human womb, and the transport or receipt of an animal chimera for any purpose. Penalties for violations of this bill include fines and/or imprisonment of up to 10 years. The bill was referred to the Subcommittee on Crime, Terrorism, Homeland Security, and Investigations on October 11, 2016, but died there. [49]
In the U.S., efforts into creating a chimeric entity appeared to be legal when the topic first came up. Developmental biologist Stuart Newman, a professor at New York Medical College in Valhalla, N.Y., applied for a patent on a human-animal chimera in 1997 as a challenge to the U.S. Patent and Trademark Office and the U.S. Congress, motivated by his moral and scientific opposition to the notion that living things can be patented at all. Prior legal precedent had established that genetically engineered entities, in general, could be patented, even if they were based on beings occurring in nature. [50] After a seven-year process, Newman's patent finally received a flat rejection. The legal process had created a paper trail of arguments, giving Newman what he claimed was a victory. The Washington Post ran an article on the controversy that stated that it had raised "profound questions about the differences—and similarities—between humans and other animals, and the limits of treating animals as property." [50]
Hybrid embryos are embryos created by mixing human sperm and animal ova, or animal sperm and human ova. Human chimera embryos are human embryos that have had animal cells added to them during early development. … Lastly, transgenic human embryos are human embryos that have had animal genes inserted into them early in development.
Another form of chimera is the mosaic, which is a composite individual derived from a single fertilized egg.
A chimera is an organism whose cells are derived from two or more zygotes as opposed to a mosaic whose different cell lines are derived from a single zygote
In the current embryological (which is also the classical) sense, a "chimaera" is an organism whose cells derive from two or more distinct zygote lineages, and this is the sense which the term "genetical chimaera" is here intended to convey. "Genetical mosaic" is less suitable, because a mosaic is formed of the cells of a single zygote lineage.
Mosaicism originates by intrinsic genetic variations caused, among other processes, by somatic mutations, while chimerism originates from allogenic fusion or grafting. As such, chimerism is much rarer and involves a much larger genetic change than mosaicism.
Many people assume this is how all intersex people came to be. My mom even said when I was a baby, people hypothesized that I was twins (I'm not). Chimeras seem to play into an old cultural myth that a "hermaphrodite" must essentially be two people
No species of mammal is hermaphroditic.
Animals are less often hermaphrodites-no mammals or birds are so
Of note, the otherwise well-studied insects, birds, and mammals are strikingly absent here—with not a single species among these groups showing hermaphroditism (for details on a supposedly hermaphroditic scale insect, however, see Gardner and Ross, 2011).
Hermaphroditism is rare in vertebrates; fish are the most advanced forms that display it, and it does not occur in mammals except as partial hermaphroditism resulting from natural or experimentally imposed hormone imbalance
No cases of hermaphroditism or parthenogenesis are found among birds and mammals.
But although hermaphroditism is common among invertebrates and occurs in some fish and other vertebrates, contrary to urban legends, human hermaphrodites do not exist.
In the past, the term hermaphrodite was widely applied in such cases, but humans are not hermaphroditic. In a truly hermaphroditic species, individuals have functional sets of male and female organs.
Hermaphroditism in the strict sense of the term does not exist in the human species. … may be equipped with both masculine and feminine gonads always more or less abnormal, incapable of simultaneously producing male and female gametes and not functional. This abnormal individual is therefore not a hermaphrodite but an intersex individual.
they certainly do not possess the complete and active sexual organs of both sexes, and so are not true hermaphrodites: they are known as false or pseudo-hermaphrodites … These false hermaphrodites may appear to possess the genital organs of both sexes, but they do not really do so.
It is now considered pejorative and outdated, although a small number of intersex people have reclaimed the term.
Some intersex people have reclaimed this word for themselves, but it is usually considered a slur. … it is not possible for one person to have both a fully developed penis and vagina.
![]() | It has been suggested that
Human Chimerism be
merged into this article. (
Discuss) Proposed since May 2024. |
A human chimera is a human with a subset of cells with a distinct genotype than other cells, that is, having genetic chimerism. In contrast, an individual where each cell contains genetic material from a human and an animal is called a human–animal hybrid, while an organism that contains a mixture of human and non-human cells would be a human-animal chimera. [1]
Some consider mosaicism to be a form of chimerism, [2] while others consider them to be distinct. [3] [4] [5]
Mosaicism involves a mutation of the genetic material in a cell, giving rise to a subset of cells that are different from the rest.
Natural chimerism is the fusion of more than one fertilized zygote in the early stages of prenatal development. It is much rarer than mosaicism. [5]
In artificial chimerism, an individual has one cell lineage that was inherited genetically at the time of the formation of the human embryo and the other that was introduced through a procedure, including organ transplantation or blood transfusion. [6] Specific types of transplants that could induce this condition include bone marrow transplants and organ transplants, as the recipient's body essentially works to permanently incorporate the new blood stem cells into it.
Natural chimerism has been documented in humans in several instances.
Human-animal chimeras include humans having undergone non-human to human xenotransplantation, which is the transplantation of living cells, tissues or organs from one species to another. [17] [18]
Patient derived xenografts are created by xenotransplantation of human tumor cells into immunocompromised mice, and is a research technique frequently used in pre-clinical oncology research. [19]
Non-artificial chimerism has traditionally been considered to be rare due the low amount of reported cases in medical literature. [27] However, this may be due to the fact that humans might not often be aware of this condition to begin with. There are usually no signs or symptoms for chimerism other than a few physical symptoms such as hyper-pigmentation, hypo-pigmentation, Blaschko's lines, body asymmetry or heterochromia iridum (possessing two different colored eyes). [28] However, these signs do not necessarily mean an individual is a chimera and should only be seen as possible symptoms. Again, forensic investigation or curiosity over an unexpected maternity/paternity DNA test result usually leads to the accidental discovery of this condition. By simply undergoing a DNA test, which usually consists of either a swift cheek swab or a blood test, the discovery of the once unknown second genome is made, therefore identifying that individual as a chimera. [29]
The concept of a "human hermaphrodite" resulting from chimerism is largely a misconception. [30] Most intersex individuals are not chimeras, [31] [30] and most human chimeras are not observed to have intersex traits. [30] Theoretically, if a gynandromorphic human chimera were to have fully functioning male and female gonad tissue, such an individual could self-fertilize; [32] [33] this hypothesis is backed by the fact that hermaphroditic animal species commonly reproduce in this way, and it has been observed in a rabbit. [34] However, no such case of functional self-fertilization has ever been documented in humans; [35] and it is non-existent or extremely rare in mammals, [36] [37] [38] [39] [40] especially in humans. [41] [42] [43] [44] While humans are known to have sex characteristics that diverge from typical males or typical females, these individuals fall under the social umbrella of intersex conditions and traits, and some consider the term "hermaphrodite" to be a slur when applied to them. [45] [46] [47]
On 11 July 2005, a bill known as The Human Chimera Prohibition Act was introduced into the United States Congress by Senator Samuel Brownback; however, it died in Congress sometime in the next year. The bill was introduced based on findings that science has progressed to the point where human and nonhuman species can be merged to create new forms of life. Because of this, ethical issues may arise as the line blurs between humans and other animals, and according to the bill with this blurring of lines comes a show of disrespect for human dignity. The final claim brought up in The Human Chimera Prohibition Act was that there is an increasing amount of zoonotic diseases. With that being said, the creation of human-animal chimeras can allow these diseases to reach humans. [48]
On 22 August 2016, another bill, The Human-Animal Chimera Prohibition Act of 2016, was introduced to the United States House of Representatives by Christopher H. Smith. It identifies a human-animal chimera as:
The bill prohibits the attempts to create a human-animal chimera, the transfer or attempt to transfer a human embryo into a nonhuman womb, the transfer or attempt to transfer a nonhuman embryo into a human womb, and the transport or receipt of an animal chimera for any purpose. Penalties for violations of this bill include fines and/or imprisonment of up to 10 years. The bill was referred to the Subcommittee on Crime, Terrorism, Homeland Security, and Investigations on October 11, 2016, but died there. [49]
In the U.S., efforts into creating a chimeric entity appeared to be legal when the topic first came up. Developmental biologist Stuart Newman, a professor at New York Medical College in Valhalla, N.Y., applied for a patent on a human-animal chimera in 1997 as a challenge to the U.S. Patent and Trademark Office and the U.S. Congress, motivated by his moral and scientific opposition to the notion that living things can be patented at all. Prior legal precedent had established that genetically engineered entities, in general, could be patented, even if they were based on beings occurring in nature. [50] After a seven-year process, Newman's patent finally received a flat rejection. The legal process had created a paper trail of arguments, giving Newman what he claimed was a victory. The Washington Post ran an article on the controversy that stated that it had raised "profound questions about the differences—and similarities—between humans and other animals, and the limits of treating animals as property." [50]
Hybrid embryos are embryos created by mixing human sperm and animal ova, or animal sperm and human ova. Human chimera embryos are human embryos that have had animal cells added to them during early development. … Lastly, transgenic human embryos are human embryos that have had animal genes inserted into them early in development.
Another form of chimera is the mosaic, which is a composite individual derived from a single fertilized egg.
A chimera is an organism whose cells are derived from two or more zygotes as opposed to a mosaic whose different cell lines are derived from a single zygote
In the current embryological (which is also the classical) sense, a "chimaera" is an organism whose cells derive from two or more distinct zygote lineages, and this is the sense which the term "genetical chimaera" is here intended to convey. "Genetical mosaic" is less suitable, because a mosaic is formed of the cells of a single zygote lineage.
Mosaicism originates by intrinsic genetic variations caused, among other processes, by somatic mutations, while chimerism originates from allogenic fusion or grafting. As such, chimerism is much rarer and involves a much larger genetic change than mosaicism.
Many people assume this is how all intersex people came to be. My mom even said when I was a baby, people hypothesized that I was twins (I'm not). Chimeras seem to play into an old cultural myth that a "hermaphrodite" must essentially be two people
No species of mammal is hermaphroditic.
Animals are less often hermaphrodites-no mammals or birds are so
Of note, the otherwise well-studied insects, birds, and mammals are strikingly absent here—with not a single species among these groups showing hermaphroditism (for details on a supposedly hermaphroditic scale insect, however, see Gardner and Ross, 2011).
Hermaphroditism is rare in vertebrates; fish are the most advanced forms that display it, and it does not occur in mammals except as partial hermaphroditism resulting from natural or experimentally imposed hormone imbalance
No cases of hermaphroditism or parthenogenesis are found among birds and mammals.
But although hermaphroditism is common among invertebrates and occurs in some fish and other vertebrates, contrary to urban legends, human hermaphrodites do not exist.
In the past, the term hermaphrodite was widely applied in such cases, but humans are not hermaphroditic. In a truly hermaphroditic species, individuals have functional sets of male and female organs.
Hermaphroditism in the strict sense of the term does not exist in the human species. … may be equipped with both masculine and feminine gonads always more or less abnormal, incapable of simultaneously producing male and female gametes and not functional. This abnormal individual is therefore not a hermaphrodite but an intersex individual.
they certainly do not possess the complete and active sexual organs of both sexes, and so are not true hermaphrodites: they are known as false or pseudo-hermaphrodites … These false hermaphrodites may appear to possess the genital organs of both sexes, but they do not really do so.
It is now considered pejorative and outdated, although a small number of intersex people have reclaimed the term.
Some intersex people have reclaimed this word for themselves, but it is usually considered a slur. … it is not possible for one person to have both a fully developed penis and vagina.