INBREEDING AND ITS CONSEQUENCES

Trừ khi quí vị cố gắng tạo ra một giống nòi của đám siêu khật khùng, còn không đừng “thuần chủng giao hợp” (Unless you’re trying to create a race of super morons. don’t do it)

Theo kết quả nghiên cứu khoa học sinh hóa di truyền, thì không chỉ loạn luân trực tiếp (con cái sinh ra do liên hệ tình dục trực tiếp giữa cha con, mẹ con, anh chị em một nhà) mà những hôn phối giữa các anh chị em chú bác, cô cậu (1đời) cũng đưa đến kết quả dị dạng và tật nguyền trí tuệ. Điển hình như trong những cộng đồng “thuần chủng truyền thống” như người Amish, Mormon (ở Mỹ), các cộng đồng Hồi giáo truyền thống như ở Pakistan, Trung Đông, và Ấn vẫn còn giữ “truyền thống anh chị em thúc bá cô cậu lấy nhau” (Inbreeding first cousins) để bảo vệ giòng tộc!

Trường hợp “nổ tiếng” nhất còn giữ lại hình ảnh sử liệu là vua Charles II của Spain với cái quai hàm dị dạng được gọi là The Habsburg Jaw. Chúng ta biết rằng các đám “quí tộc” thường tối dạ trong trò bảo vệ giống nòi này. Quí vị không tin, hãy nhìn kỹ gia đình nữ hoàng Anh hiện nay sẽ thấy!!!

Có một điều mà mọi người chúng ta khi có cơ hội đi du lịch khắp nơi về vùng sâu vùng xa thường hay thắc mắc nho nhỏ: Đó là hầu như trong những  nhóm cư dân nhỏ sống xa xôi thường xuất hiện những khuôn mặt xấu xí, dị dạng và hành xử không được bình thường, hoặc kém thông minh nhanh nhẹn! Phải chăng đây là hệ quả của “hôn nhân nội tộc” (inbreeding) do thiếu điều kiện giao tiếp mở rộng với xã hội lớn hơn???

Hiện nay, chúng ta đều có thể thấy tận mắt những hệ quả “thuần chủng giống nòi” này ở những nhóm người Amish, Mormons bên Mỹ, và tại các nhóm người Hồi ở tiểu Á.
Tại Việt Nam, ngoài những “dị dạng” chưa xác định của các cư dân vùng sâu vùng xa, chúng ta không có một nghiên cúu chứng tích nghiêm túc nào về những con cháu “giòng dõi” nhà Trần. Nếu hình ảnh vua chúa để lại chắc chắn các họa sĩ thời đó  phải vẽ “đẹp và uy nghi”, bố bảo dám vẽ đúng chân dung công chúa, hoàng tử vương hầu chính xác dị dạng… Tội “khi quân phạm thượng” là tru di tam tộc, hay ít ra là bị trảm!!!  Chính sử văn minh Á Châu Tầu Việt phải luôn là tốt đẹp và vĩ đại! Và cái văn hóa “tốt khoe xấu che” nó không thể đẻ ra và để lại  những văn bản, hình ảnh chân dung chứng sử đúng đắn được nữa. Cứ nhìn cái hình của tên phỉ già Hồ chí Minh được treo chính thức các nơi khi đem so với hình ảnh thời sự thì rõ.. Nó đã  được các “họa sĩ, nhiếp ảnh gia ái quốc” Việt Nam tư sửa thêm bớt sao cho tên phỉ “Bác Hồ” của chúng nhìn PHÚC HẬU!!!

Nói tóm gọn lại, là khoa học đã xác minh  từ những bằng chứng cụ thể trên, rằng những câu chuyện sử hay những tuyên bố tự hào về sự TINH HOA THUẦN CHỦNG GIỐNG NÒI DÂN TỘC là hoàn toàn hoang tưởng! Không có xã hội nào thuần chủng hết. Vì giả sử THUẦN CHỦNG THẬT  thì đám con cháu sẽ toàn là một lũ tật nguyền dị dạng và khật khùng kém trí tuệ hết cả. DNA đã cho biết xã hội nhóm người nào cũng đều tạp chủng vì người ta di chuyển buôn bán làm ăn, tìm đất mới sau những thiên tai cũng như chiến tranh xảy ra.. và cứ hàng qua ngàn năm như thế.. sự pha trộn xảy ra cao và thường hơn khi điều kiện giao tiếp di chuyển càng ngày càng thuận tiện mở rộng.

Chỉ cần nhìn lại ngay Viêt Nam thôi, cái gọi là giống “đậu phọng đỏ” cũng đầy những người đến từ Tầu, Miên, Thái, Lào, Ấn v,v chưa kể những sắc dân Chàm, thượng.. Và sau thời thực dân, thì đã thêm đủ mầu sắc từ Phi Châu và Âu Mỹ…Đây là một tiến trình tích cực. tận dụng được tiến trình này, sẽ nâng được đòi sống và nhận thức xã hội tốt hơn.

NKPTC

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The broad scientific definition of inbreeding is that it is the mating of individuals more closely related to each other than the average relationship within the population concerned. This statement is really only valid for large populations, since with small populations inbreeding is inevitable, even with random mating. To be more precise, an inbred person is defined as someone whose parents are related. In practice this means close direct relationship or, more usually, related through recent common ancestors, since all members of the same species are related to some extent.

The adverse effects of inbreeding in animals are well known. The incidence of metabolic disorders, structural abnormalities and inherited disease conditions, caused by harmful recessive genes, increases following inbreeding. Performance in several characters, particularly those concerned with reproduction and survival, declines following the mating of close relatives. This is known as inbreeding depression. These effects are mainly due to an increase in the frequency of homozygous genotypes(AA and aa) at the expense of heterozygotes (Aa), which is caused by inbreeding. It is only harmful, however, when the dominance is directional, which means that the undesirable member of a pair of genes is usually recessive. When a high proportion of these harmful genes are present in the heterozygous state (Aa) the animal is protected from their debilitating effects by the dominance of the normal gene; but when some of the heterozygotes are replaced by homozygous recessives (aa), following inbreeding, their harmful effects become manifest. Other types of gene action are sometimes responsible for inbreeding damage, but are thought to be less important. These are: overdominance, epistatic interaction and the overall level of heterozygosity.

Overdominance occurs when the heterozygote (A1A2) is superior in performance to either of the two homozygotes (A1A1 or A2A2). In this situation, an increase in homozygosity following inbreeding also causes inbreeding depression.
Epistatic interaction between different pairs of genes occurs when one pair affects the expression of another pair at a different locus. With one particular type, called complementary epistasis, two dominants, one from each of two separate loci, are necessary for normal development or metabolism,Thus, AABB, AaBB, AABb and AaBb will be normal, but AAbb, aaBB Aabb, aaBb and aabb will be defective. This situation arises when a metabolic pathway requires two enzymes for the essential end-product to be synthesised. Since each enzyme requires a different dominant gene for its synthesis, the absence of one or both will result in a defective individual. Inbreeding in a population with a mixture of the above genotypes will lead to a break-up of the favourable gene combinations, with more inferior genotypes, particularly aaBB, AAbb and aabb, being produced.
Finally, Lerner (1954) found evidence that some abnormal conditions in animals were not caused by single genes but by a drop in the general level of heterozygosity throughout the whole genome. His theory of developmental homeostasis suggests that for an animal to be able to cope with developmental accidents and environmental stress there is a minimum or obligate level of heterozygosity for normal development. The implication being that heterozygotes in general are more versatile because they can produce a greater variety of enzymes and other proteins. This means that the heterozygosity level per se, as well as the effects of the genes themselves, may be a contributing factor.

The opposite of inbreeding depression is known as heterosis or hybrid vigour and can result from the crossing of unrelated inbred animals or lines with different genetic backgrounds. What is lost from inbreeding is usually restored when several inbred lines are crossed randomly. Deliberate inbreeding and crossing, followed by selection between lines, is sometimes used with farm plants and animals to improve yields. Its significance in humans is that greater mobility means that people travel further to find a spouse and are less likely to marry a person from the same locality with a similar genotype. Thus, although most of the increase in height and improved survival is the result of better nutrition and disease control, a small part may also be due to heterosis following a change in the mating system.

FORBIDDEN MARRIAGE LAWS OF THE UNITED KINGDOM

In England the list of forbidden marriages was drawn up by the Church of England in 1560 and remained unchanged until the 20thcentury. I have reproduced the original list below. Because it is presented in a precise but rather complicated way I have transformed the list into a more easily understood form here .
A TABLE OF KINDRED AND AFFINITY [17]
WHEREIN WHOSOEVER ARE RELATED ARE FORBIDDEN IN SCRIPTURE AND OUR LAWS TO MARRY TOGETHER
A Man may not marry his
A Woman may not marry her
1 Grandmother
1 Grandfather
2 Grandfather’s Wife
2 Grandmother’s Husband
3 Wife’s Grandmother
3 Husband’s Grandfather
4 Father’s Sister
4 Father’s Brother
5 Mother’s Sister
5 Mother’s Brother
6 Father’s Brother’s Wife
6 Father’s Sister’s Husband
7 Mother’s Brother’s Wife
7 Mother’s Sister’s Husband
8 Wife’s Father’s Sister
8 Husband’s Father’s Brother
9 Wife’s Mother’s Sister
9 Husband’s Mother’s Brother
10 Mother
10 Father
11 Stepmother
11 Stepfather
12 Wife’s Mother
12 Husband’s Father
13 Daughter
13 Son
14 Wife’s Daughter
14 Husband’s Son
15 Son’s Wife
15 Daughter’s Husband
16 Sister
16 Brother
17 Wife’s Sister
17 Husband’s Brother
18 Brother’s Wife
18 Sister’s Husband
19 Son’s Daughter
19 Son’s Son
20 Daughter’s Daughter
20 Daughter’s Son
21 Son’s Son’s Wife
21 Son’s Daughter’s Husband
22 Daughter’s Son’s Wife
22 Daughter’s Daughter’s Husband
23 Wife’s Son’s Daughter
23 Husband’s Son’s Son
24 Wife’s Daughter’s Daughter
24 Husband’s Daughter’s Son
25 Brother’s Daughter
25 Brother’s Son
26 Sister’s Daughter
26 Sister’s Son
27 Brother’s Son’s Wife
27 Brother’s Daughter’s Husband
28 Sister’s Son’s Wife
28 Sister’s Daughter’s Husband
29 Wife’s Brother’s Daughter
29 Husband’s Brother’s Son
30 Wife’s Sister’s Daughter
30 Husband’s Sister’s Son
Wherein whosoever are related are forbidden in scripture and our laws to marry together
A Man may not marry his
A Woman may not marry her
1 Grandmother
1 Grandfather
2 Stepgrandmother
2 Stepgrandfather
3 Grandmother-in-Law
3 Grandfather-in-Law
4-5 Aunt
4-5 Uncle
6-9 Aunt-in-Law
6-9 Uncle-in-Law
10 Mother
10 Father
11 Stepmother
11 Stepfather
12 Mother-in-Law
12 Father-in-Law
13 Daughter
13 Son
14 Stepdaughter
14 Stepson
15 Daughter-in-Law
15 Son-in-Law
16 Sister
16 Brother
17-18 Sister-in-Law
17-18 Brother-in-Law
19-20 Granddaughter
19-20 Grandson
21-22 Granddaughter-in-Law
21-22 Grandson-in-Law
23-24 Stepgranddaughter
23-24 Stepgrandson
25-26 Niece
25-26 Nephew
27-30 Niece-in-Law
27-30 Nephew-in-Law
No cousins are mentioned, which is surprising since double first cousins (first degree and normal) are equivalent in their relationships to full and half sibs respectively. Also, half sibs are not mentioned, but I think the inclusion of half sibs is implicit in the general terms ‘brother’ or ‘sister’.In the same vein half uncles, half aunts, half nephews and half nieces are implicitly included with their full counterparts.This is made clearer in later lists where half sibs are referred to specifically.
The full set of in-laws and step relatives are included to match the equivalent blood relatives of the same name except the following:
Stepsister Stepbrother
Stepaunt Stepuncle
Stepniece Stepnephew
It seems strange excluding stepbrothers and stepsisters while including stepsons and stepdaughters. The first changes were made in 1907:
The 1907 Marriage Act removed no. 17 from the forbidden list (Wife’s sister and Husband’s brother), provided the first spouse in each case was deceased. Further changes followed in 1921, 1931 and 1949:
The 1921 Marriage Act removed no. 18 (Brother’s wife and Sister’s husband) provided brother or sister in each case was deceased.
The 1931 Marriage Act removed 6, 7, 8 and 9 (Aunt-in-law and Uncle-in-law) and 27, 28, 29 and 30 (Niece-in-law and Nephew-in-law), provided the relevant Uncle, Aunt, Niece, and Nephew were dead.
The 1949 Marriage Act confirmed the previous 3 acts and specifically included ‘half blood’ relatives.
A TABLE OF KINDRED AND AFFINITY [18]
WHEREIN WHOSOEVER ARE RELATED ARE FORBIDDEN BY THE CHURCH OF ENGLAND TO MARRY TOGETHER
A man may not marry his:
A woman may not marry her:
1 Mother
1 Father
2 Daughter
2 Son
3 Father’ Mother
3 Father’s Father
4 Mother’s Mother
4 Mother’s Father
5 Son’s Daughter
5 Son’s Son
6 Daughter’s daughter
6 Daughter’s son
7 Sister
7 Brother
8 Father’s Daughter
8 Father’s Son
9 Mother’ Daughter
9 Mother’s Son
10 Wife’s Mother
10 Husband’s father
11 Wife’s Daughter
11 Husband’s Son
12 Father’s Wife
12 Mother’s Husband
13 Son’s Wife
13 Daughter’s Husband
14 Father’s Father’s Wife
14 Father’s Mother’s Husband
15 Mother’s Father’s Wife
15 Mother’s Mother’s Husband
16 Wife’s Father’s Mother
16 Husband’s Father’s Father
17 Wife’s Mother’s Mother
17 Husband’s Mother’s father
18 Wife’s Son’s Daughter
18 Husband’s Son’s Son
19 Wife’s Daughter’s Daughter
19 Husband’s Daughter’s Son
20 Son’s Son’s Wife
20 Son’s Daughter’s Husband
21 Daughter’s Son’s Wife
20 Daughter’s Daughter’s Husband
22 Father’s Sister
22 Father’s Brother
23 Mother’s Sister
23 Mother’s Brother
24 Brother’s Daughter
24 Brother’s Son
25 Sister’s Daughter
25 Sister’s Son
A man may not marry his:
A woman may not marry her:
1 Mother
1 Father
2 Daughter
2 Son
3-4 Grandmother
3-4 Grandfather
5-6 Granddaughter
5-6 Grandson
7 Sister
7 Brother
8-9 Half Sister
8-9 Half Brother
10 Mother-in-Law
10 Father-in-Law
11 Stepdaughter
11 Stepson
12 Stepmother
12 Stepfather
13 Daughter-in-Law
13 Son-in-Law
14-15 Stepgrandmother
14-15 Stepgrandfather
16-17 Grandmother-in-Law
16-17 Grandfather-in Law
18-19 Stepgranddaughter
18-19 Stepgrandson
20-21 Granddaughter-in-Law
20-21 Grandson-in-Law
22-23 Aunt and Half Aunt
22-23 Uncle and Half Uncle
24-25 Niece and Half Niece
24-25 Nephew and Half Nephew
To emphasise that the ten ‘in-law’ relatives, removed from the above list, could only marry the nominated person if all previous spouses were dead, a second list was included:
1. Deceased wife’s sister
1. Deceased sister’s husband
2. Deceased brother’s wife
2. Deceased husband’s brother
3. Deceased wife’s brother’s daughter
3. Deceased husband’s brother’s son
4. Deceased wife’s sister’s daughter
4. Deceased husband’s sister’s son
5. Brother’s deceased son’s wife
5. Brother’s deceased daughter’s husband
6. Sister’s deceased son’s wife
6. Sister’s deceased daughter’s husband
7. Father’s deceased brother’s wife
7. Father’s deceased sister’s husband
8. Mother’s deceased brother’s wife
8. Mother’s deceased sister’s husband
9. Deceased wife’s father’s sister
9. Deceased husband’s father’s brother
10. Deceased wife’s mother’s sister
10. Deceased husband’s mother’s brother
1-2 Sister-in-law
1-2 Brother-in-law
3-6 Niece-in-law
3-6 Nephew-in-law
7-10 Aunt-in-law
7-10 Uncle-in-law
Current Regulations (1986)
Since 1949 there have been several further Marriage Acts culminating in the 1986 Act which brought the regulations up to date.
Blood Relatives
The following blood relatives are still forbidden to marry under all circumstances:
A man may not marry his:
A woman may not marry her:
Mother
Father
Daughter
Son
Grandmother
Grandfather
Granddaughter
Grandson
Sister
Brother
Half Sister
Half Brother
Aunt
Uncle
Half Aunt
Half Uncle
Niece
Nephew
Half Niece
Half Nephew
In 1960 the restrictions on the in-law relatives mentioned in tables 26 and 27 were removed. This means they are now free to marry irrespective of whether the former spouse is dead. i.e. It allows divorcees in this category to remarry.
The following in-laws can also marry without any restrictions, i.e. regardless of whether or not their first spouses are still alive:
A man can marry his:
A woman can marry her:
Former wife’s father’s mother
(Grandmother-in-law)
Former husband’s father’s father
(Grandfather-in-law)
Former wife’s mother’s mother
(Grandmother-in-law)
Former husband’s mother’s father
(Grandfather-in-law)
Son’s son’s former wife
(Granddaughter-in-law)
Son’s daughter’s former husband
(Grandson-in-law)
Daughter’s son’s former wife
(Granddaughter-in-law)
Daughter’s daughter’s former husband
(Grandson-in-law)
The remaining step relatives can now marry provided they are over 21. Also, the younger person must not have been treated as a child of the older person’s family and never, under the age of 18, lived under the same roof as the older person.
A man can marry his:
A woman can marry her:
Former wife’s daughter
(Stepdaughter)
Former husband’s son
(Stepson)
Father’s former wife
(Stepmother)
Mother’s former husband
(Stepfather)
Father’s father’s former wife
(Stepgrandmother)
Father’s mother’s former husband
(Stepgrandfather)
Mother’s father’s former wife
(Stepgrandmother)
Mother’s mother’s former husband
(Stepgrandfather)
Former wife’s son’s daughter
(Stepgranddaughter)
Former husband’s son’s son
(Stepgrandson)
Former wife’s daughter’s daughter
(Stepgranddaughter)
Former husband’s daughter’s son
(Stepgrandson)
The remaining in-laws can now also marry provided they are both over 21 and any former spouses must be deceased.
A man can marry his:
A woman can marry her:
Former wife’s mother
(Mother-in-law)
Former husband’s father
(Father-in-law)
Son’s former wife
(Daughter-in-law)
Daughter’s former husband
(Son-in-law)
A new forbidden category has now been added covering adopted children:
A man may not marry his:
A woman may not marry her:
Adoptive mother or former adoptive mother
Adoptive father or former adoptive father
Adopted daughter or former adopted daughter
Adopted son or former adopted son
Surprisingly marriage between unrelated adopted brothers and sisters (i.e. adopted by the same adoptive parents) is allowed.
The marriage laws for Scotland and Northern Ireland are similar to England and Wales except that Scotland also includes the following forbidden blood relationships:
A man may not marry his:
A woman may not marry her:
Great-grandmother
Great-grandfather
Great-granddaughter
Great-grandson
Comments on the 1986 Regulations
My criticism is that there are still no sensible rules about marriage between ‘blood’ relatives. The only logical way would be to fix an obligate level of inbreeding beyond which it is not permissible to go. For example, if the maximum coefficient of relationship between partners is fixed at 1/8, this would limit the coefficient of inbreeding to 1/16 (6.25%). Marriages between single first cousins would then still be allowed but not between double first cousins. It would also allow unions between half uncle and half niece and between half aunt and half nephew. If this was introduced the list of forbidden marriages between’blood’ relatives would then become:
Relationship
R
Parent-child
1/2
Full Sib
1/2
Half Sib
1/4
Double First Cousins (first degree)
1/2
Double First Cousins
1/4
Grandparent-grandchild
1/4
Uncle-niece and Aunt-nephew
1/4
Also any other unusual cousin or other relationships with an R value of 1/4 or above (see enhanced relationships.)
These figures could only be used as a guide since previous inbreeding (known or unknown), particularly in small closed populations could cause nominally low relationships such as first cousin (R = 1/8) to rise above 1/4. In these special situations it would be necessary to have a genetically qualified panel to assess the wisdom of certain marriages. The presence of any known inherited abnormalities in a family would also have to be taken into account.

Incest
Incest is defined by Martin (1990) as: ”Sexual intercourse between a man and his mother, daughter, sister, half sister or granddaughter, or between a woman over the age of 16 and her father, son, brother, half brother or grandfather. Even if both partners consent, incest is a criminal offence if the partners know of their relationship. It is punishable by up to 7 years imprisonment (or, with a girl under 13, by a maximum sentence of life imprisonment), but no prosecution can be brought without the consent of the Director of Public Prosecutions. The relationships listed above include illegitimate relationships. It is a statutory offence for a man to incite a girl to have incestuous intercourse with him, but being under 16, she would not be guilty of any crime if intercourse took place.”
Comments
Apart from religious constraints, the idea that incest laws should only encompass members of the close family stems from the desire to protect vulnerable children. From the biological point of view, however, all close inbreeding is harmful and undesirable, even when it involves relatives outside the nuclear family.
The above list excludes several relationships which are as close or even closer, in terms of the coefficient of relationship, than those within it. The following are some examples:
  • Grandmother-grandson. This is a sexist exclusion, since although Grandfather-granddaughter incest is more likely to happen, when Grandmother-grandson incest does occur it is just as serious.
  • Uncle-niece and Aunt-nephew sexual unions are excluded even though their coefficients of relationship are the same as between Half sibs and Grandfather-granddaughter (R = 1/4).
  • Double first cousins of both types (first degree and normal), with R values equal to Full and Half sibs respectively, are also excluded. Likewise any of the other unusual cousin relationships described earlier, with coefficients of relationship of 1/4 or above. In view of the severity of the punishment for statutory incest I think these close cousin relationships should at least be included among the list of forbidden marriages.
[18] 1955 edition of the Book of Common Prayer (Church of England)
[17] Taken from the 1908 edition of The Book of Common Prayer (Church of England)
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