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ANNALS OF HUMAN BIOLOGY) 1991, VOL. 18, NO. 1, 31-46
Genetic demography of the Moscow population: migration, outbreeding and assortative mating
O. L. KURBATOVA and E. Yu. POBEDONOSTSEVA
N.I. Vavilov Institute of General Genetics, USSR Academy of Sciences, Moscow, USSR
Received 16February 1989; revised 11 June 1990
Summary. Using marriage records, census data, and other statistical sources, some demo- graphic parameters of Moscow population in 1955 and 1980 have been studied, such as age at marriage, birthplace, nationality and profession of permanent residents. Migration has been shown to be the main factor of Moscow population dynamics. Genetically significant, quantitative and geographic parameters of this process have been obtained (migration rates, migration and marital distances, proportion of interethnic marriages). During the past two centuries the mean distance travelled by migrants, arriving in Moscow, increased by several times, the genetic contribution from eastern and southern parts of the country being especially marked. In the period of maximum migration rates the percentage share of marriages between Moscow-born people was only 10070. The percentage share of interethnic marriages was 14-75070 in 1955 and 16"53070 in 1980. The degree of isolation by distance, predicted by Mal6cot's model, appeared to be quite low. Positive assortative mating for nationality, birthplace, age and profession was characterized as a factor, counteracting outbreeding. While the deleterious effects of isolation and inbreeding are well known, the genetic consequences of alternative state are still obscure.
1. Introduction The attention of human population geneticists has traditionally been focused on
populations of small size (the so-called "anthropological isolates"); they represent an appropriate model for studying genetic drift and the consequences of isolation and inbreeding. However, the adaptive structure of such populations, formed during previous evolutionary history, is now being destroyed as a result of social progress, increasing migration and urbanization (Coleman 1982). Taking its place, population structure of a new type has arisen in modern conurbations, distinguished from the traditional pattern by a number of genetically significant parameters: large population size; a complicated infrastructure; predominant migration pressure from without, resulting in enlargement of the marriage circle; and new socio-ecological parameters producing changes in the specificity of mutation processes and adaptation to the changing environment (Kurbatova 1975, Kurbatova, Pobedonostseva and Imasheva 1984a). All of these features are intrinsic to Moscow, the largest urban centre in the USSR, and an ancient city first mentioned in the chronicles of 1147. Migration and the absorption of neighbouring settlements were the main and often the only sources of growth in the population of Moscow (Khorev and Kiseleva 1982). At present Moscow has 9 million residents, several more million inhabitants live in the outer suburbs of the city, linked to the centre by intensive commuting.
In previous studies it has been shown that the Moscow population gene pool is rapidly being replaced as part of the process of a genetically and ethnically differentiated population influx from all regions of the USSR; the capital has tended to become the panmixia centre for the whole population of the country (Kurbatova 1975, Kurbatova and Rychkov 1978, Rychkov 1979). At the same time there is significant positive assortative mating for some demographic parameters, and there is significant positive assortative mating counteracting the effects of outbreeding (Kurbatova and
0301--4460/91 $3.00 © 1991 Taylor & Francis Ltd.
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32 D.L. Kurbatova and E. Yu. Pobedonostseva
Pobedonostseva 1988a,b). In the present paper the marriage structure of the Moscow population is considered with the aim of comparing the role of migration and assortative mating.
2. Materials and methods Marriage certificates for all couples registered in a marriage office of one of the
Moscow districts in 1955 (3485 pairs) and in 1980 (2676 pairs) have been analysed. The following data on brides and grooms were considered in the analysis: age at marriage, birthplace, residence, nationality, profession. Marriages between non-permanent residents of the capital were excluded from further consideration.
Statistical data on the demography of the late nineteenth and early twentieth centuries and current statistics were also used for comparative purposes. Data were treated by conventional statistical methods. The degree of assortative mating for quantitative characters (age) was measured by correlation coefficient r, for qualitative traits (nationality, birthplace, profession)ruby contingency coefficient
K= N.x/(a- 1)(b- 1)
where a,b = the number of rows and columns in the contingency table, and N = the number of pairs (Lakin 1980). The basic migration parameters have been evaluated using Mal6cot's model of isolation by distance (see Morton 1977).
3. Results
Migration The decisive factor in Moscow population dynamics during its centuries-old history
was the pressure of centripetal (from the periphery to the capital) migration. Among those married in 1955 Moscow-born persons amounted to only 24o70, while in 1980 the figure had risen to 60o70, the proportions in each case being almost equal for brides and grooms (table 1). Since the mean age at marriage was almost the same as the generation length (25-30 years), we can estimate the coefficient of migration to Moscow by the proportion of migrants among the newly-weds. The migration coefficient thus defined was 0.76 in 1955 and 0.40 in 1980.
In the late nineteenth and early twentieth centuries 20-25°7o of men and 33O7o of women living in Moscow were Moscow-born (Rashin 1956). The coefficient of immigration to Moscow fluctuated over this period close to 0" 6, reaching a maximum value during the years preceding the First World War (see table 2). These unusually high
Table 1. Birthplaces of people married in Moscow in 1955 and 1980.
Birthplace 1955 1980
Men Women Men Women Moscow 710 (22.42%0) 787 (24.85%) 1442 (60-97%) 1378 (58"27%) Another place
in the USSR 2457 (77.58%) 2380 (75.15%) 923 (39-03%) 987 (41.73%)
Total 3167 2365
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Genetic demography of the Moscow population
Table 2. Moscow population growth and immigration coefficients.
33
Population size Migration coefficient
Years (thousand people) (period of time)t
1871 602 0" 64 (1872-81) 1882 753 0.57 (1882-96) 1897 1039 0.61 (1897-1901) 1902 1175 0" 59 (1902-06) 1907 1346 0"86 (1907-11) 1917 2017 Not calculated 1920 1027 Not calculated 1926 2026 Not calculated 1939 4137 0" 76 (1930-55) 1956 4839 0- 52 (1948-73) 1970 7077 0.46 (1969-70) 1980 8099 0-40 (1955-80)
t For methods of estimate and sources of data see Kurbatova et al. 1984.
levels of migration corresponded to the period of uncontrolled city population growth. During the next decade of social upheaval the population of Moscow reduced by a half, but by 1926 the city regained its prewar population size due to intensive immigration (Fedotovskaya 1980). From the 1930s onwards administrative measures aimed at planned regulation of population growth have been adopted in the capital, which resulted in a gradual decline of the immigration coefficient. At the same time the origins of migrants to Moscow have drastically changed. The distribution by birthplace of migrants married in Moscow is examined separately in table 3. Here birthplaces of migrants are aggregated into large territorial units according to subdivision of the USSR into economic regions (see figure 1). Since the emigration of permanent residents from Moscow is quite uncommon, all children born to the married couples under study will contribute only to the Moscow population. Therefore from data given in table 3 we
Table 3. Distribution by birthplaces of migrants married in Moscow in 1955 and 1980.
Birthplace (region, no.)t
1955 1980
Number of Percentage Number of Percentage people people
I. Central 2756 56.98 686 35.92 2. Central Chernozem 541 ll" 18 127 6"65 3. Volga-Vyatka 267 5.52 105 5.50 4. Byelorussia 130 2.69 40 2.09 5. Baltic republics 15 0.31 20 1-05 6. Ukraine a. Moldavia 320 6"61 189 9-89 7. Volga 265 5" 48 139 7.28 8. Northwest 157 3" 24 78 4.08 9. North Caucasus 94 1-94 77 4"03
10. Urals 68 1.41 83 4-34 11. Transcaucasian republics 47 0" 97 84 4.40 12. Kazakhstan a. Kirghizia 28 0- 58 39 2.04 13. West Siberia 73 1-51 62 3"25 14. Middle Asia 25 0.52 51 2-67 15. East Siberia 27 0" 56 42 2"20 16. Far East 24 0"50 88 4-61
Total 4837 100- 0 1910 100.0
tRegion numbers correspond to those defined in figure 1; significance of difference between distributions in 1955 and 1980: X 2 = 760; p < 0.001.
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34 D . L . Kurba tova and E. Yu. Pobedonos t seva
fS
48
t6"
J
0
0 D
D
Figure 1. Economic regions of the USSR, regarded as basic territorial units in the present study of migration. 1 =Central; 2=Central Chernozem; 3=Volga-Vyatka (including Mari, Mordovian and Chuvash autonomous republics); 4 = Byelorussia; 5 = Baltic republics (Estonia, Lithuania and Latvia); 6 = Ukraine and Moldavia; 7 = Volga (including Kalmyk and Tatar autonomous republics); 8 = Northwest (including Komi and Karelian autonomous republics and Nenets autonomous area); 9 = North Caucasus (including Daghestan, Kabardin-Balkar, North-Ossetian and Chechen-Ingush autonomous republics, Adygei and Karachai-Circassian autonomous regions); 10=Urais (including Bashkir and Udmurt autonomous republics and Komi-Permyak autonomous area); 11 = Transcaucasus (Armenia, Azerbaijan and Georgia); 12=Kazakhstan and Kirghizia; 13 =West Siberia (including Khanty-Mansi and Yamalo- Nenets autonomous areas and Gorno-Altai autonomous region); 15 = East Siberia (including Buryat and Tuva autonomous republics, Khakass autonomous region, Evenki and Taimyr (Dolgano-Nenets) autonomous areas); 16 = Far East (including Y akut autonomous republic, Jewish autonomous region,
Chukchi and Koryak autonomous areas).
can estimate the genetic contribution of migrants from all economic regions to the Moscow population. It can be seen that the proportion of people born in distant regions, especially in the south and east (nos. 6, 7, 9-16) has increased in the migration flow. At the same time there was a sharp decline in the proportion of people born in the central regions, nearestto Moscow (nos. 1, 2). The mean distance travelled by migrants arriving in Moscow almost doubled over the 25-year period: in 1955 it was 562 + 9 km and in 1980 it was 1076 +_ 29 km. The dependence of migration intensity on distance in 1955 may be described by a power curve of the type y = ax b, and in 1980 by a B-distribution, accounting for the increase in long-range migration (see figure 2). For comparison we may point out that in the late nineteenth and early twentieth centuries the Moscow population increased mostly by the influx of people from indigenous Russian 'gubernias' (provinces): 80-90% of migrants arrived in Moscow were from the Moscow 'gubernia' and 'gubernias' bordering on it. The mean distance travelled by migrants was then 230 km (calculated according to Rashin 1956, Nifontov 1954).
Assuming that, for brides and grooms who contracted their marriage in Moscow, remoteness of their birthplaces from the capital corresponds to the distance between birthplaces of future parents and offspring, we can predict the basic migration
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Genetic demography of the Moscow population 35
]•'[n I000
800
600
4OO
200
300
200
I00
30000
20000
I0000
I
b
•
•OQ mm |
____..->
3lSl7 m I~ 2 4 6 9
B • v U
I I I I I
12 ]314 ]]5 {6 II
Figure 2. Intensity of migration into Moscow depending on distance from the capital of the region of departure: (a) in 1955, theoretical curve y=15.13 e-°'sSX/x(1-x); (b) in 1980, theoretical curve y=6" 13e]'37x/x(1-x); (c) in 1970, computed according to population census data, theoretical curve y = 710eX/x(l -x ) . The distance from Moscow of the region left is given on the abscissa in arbitrary units; numbers correspond to regions in figure 1, ordinate shows number of migrants arriving in Moscow per 1
million people in corresponding region left.
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36
Table 4.
D.L. Kurbatova and E. Yu. Pobedonostseva
Basic parameters of the model of isolation by distance in the Moscow population from data on distances between Moscow and birthplaces of the spouses.
Date of marriage d s m s' k m e b
1955 429±7 738 0-0081 607 0.7556 0"1109 0.0008 (n=6334) di>2950 61<di<2950
1980 434± 14 1049 0.0186 748 0"3852 0.1211 0.0006 (n=4730) dii>4200 75<di<4200
Note: d= arithmetic mean distance between birthplaces of parents and their offspring, in km; s= the central standard deviation; m=P(di>4s)--the long-range migration rate; s' =the central standard deviation for short-range migration (di<4s); k -~ ' / 10<d i<4s - - the short-range migration rate; m e = ~ ) - - t h e effective migration; b=x/2me/s'; n--number of parent-offspring pairs, in suggestion that parents' fertility does not depend on d i and is equal to 2.
parameters from Mal6cot's model of isolation by distance (table 4). In 1980 the mean parent-offspring distance appeared to be insignificantly longer than in 1955, since the above-mentioned increase in migration distance was paralleled by the decline in migration intensity (in other words, there was an increase in the proportion of Moscow- born people for whom the parent-offspring distance will be zero). At the same time, the standard deviation around zero of the distribution of parent-offspring distance is significantly higher in 1980 than in 1955. In addition, there was a greater than two-fold increase in the rate of long-range migration which, according to the model used, was defined as migration at distances >2950 km in 1955 and >4200 km in 1980 (see table 4). By comparison, the frequency of short-range migrants was twice as small in 1980 as in 1955. These estimates are, of course, rather conventional, but some parameters predicted by the model seem quite realistic; e.g. the predicted size of the Moscow locality, also given in table 4, indicates that now not only residents of the city itself, but also people living in neighbouring settlements within a radius of 61 km in 1955 and 75 km in 1980, should be referred to as part of the Moscow population (these parameters correspond to known commuter patterns: according to the Geographic Encyclopedic Dictionary published in 1983 the radius of Moscow city agglomeration is 60-70 km). Effective migration, me, appears to be several times lower than the overall migration coefficients given in table 2. The extremely small magnitude of parameter b implies an insignificant degree of isolation by distance.
In fact all these inferences, based on the assumption of a decline in genetic kinship with distance, are greatly complicated by the degree of diversity of the USSR ethnic map. Actually immigration from different regions of the USSR results in an increase in the variety of the capital's ethnic composition. The population of Moscow, as well as the populations of most ancient cities of the European part of Russia, originated from the aboriginal Slavic rural population (Rabinovich 1978) and during past centuries it was characterized by high ethnic homogeneity (table 5). According to the 1989 census, people of more than 100 nationalities inhabit Moscow. In 1955 representatives of 31 nationalities, and in 1980 those of 37 nationalities have been encountered in the studied cohort of newly-weds. The percentage shares of six nationalities, the most numerous in Moscow, are shown in table 5. The share of Russians was high and practically stable during the study period, however it is now somewhat lower than in the late nineteenth and early twentieth centuries. The Ukrainian component did not alter between 1955 and 1980; the proportions of Byelorussians and Jews have dropped whereas those of Armenians and Tatars have increased. Assuming random mating, in Moscow one can
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Genetic demography of the Moscow population
Table 5. Ethnic composit ion o f the Moscow populat ion for a number of years.
37
Years
Nationality 1955~ 1980t 18975 19025 19595 19705 19795
Russians 89.02 88" 94 95" 0 95" 3 88.6 89.2 90" 0 Ukrainians 2 .9 2.85 0 .4 0" 1 2" 3 2 .6 2- 6 Byelorussians 1.34 0" 72 0" 1 0 .0 0" 6 0 .7 0 .7 Jews 2.50 1.78 0"5 0"4 4 .7 3"6 2"9 Tatars 1.33 2.16 0 .4 0-5 1.6 1 "5 1.7 Armenians 0" 41 0" 93 0 .2 0 .2 0" 3 0 . 4 0" 4 Others 2-44 2.62 3 .4 3"5 1-8 2"0 1.7
t F r o m the data of present investigation. SFrom population census data (see Vydro 1976). Significance of difference between sample distr ibutions in 1955 and 1980; X 2 = 39.8.
encounter marriages between people originating from all the regions of the USSR, including 21070 of interethnic marriages.
Marriage structure The structure of marriages determines such basic population-genetics parameters as
the degree of endo/exogamy, inbreeding and heterozygosity that in turn are correlated with normal and pathological variation of many morphophysiological characters in humans. In the past, geographical space as well as various social, religious and ethnic barriers had a great influence on the formation of marriage structure both in urban and rural populations. In contemporary populations studies large cities such as Moscow are often considered as a model panmictic population supposing random mating for all genetically significant parameters. In practice, as suggested by the empirical data given below, mating choice involves not only age of the partner but also other demographic characters, such as nationality, birthplace and profession.
Age at marriage. Age distributions of people married either in 1955 or 1980 are characterized by marked positive skewness and positive kurtosis, but at the same time differ significantly from each other: mean age of brides increased by 1.5 years, and by 2.5 years for grooms; the variance of the distribution also increased substantially (table 6). Further analysis has shown that these differences can be attributed mainly to the increase in number of marriages at an older age: in 1955 in 3°70 of marriages at least one partner was older than reproductive age; by 1980 such couples constituted 8070 of the total (these couples were not taken into consideration in the analysis of migration). It was apparent that, in marriages between Moscow-born people, age at marriage remained practically unchanged over the 25-year period and was noticeably lower than in unions between a Moscow-born individual and a migrant or between migrants. Of the population within the reproductive phase, the age of brides averaged 25.67 ___ 0.11 in 1955 and 25.41 +_0-15 years in 1980; that of grooms 27.20___0.13 and 27-91 +0" 17 years respectively. Those younger than 20 years of age in 1955 constituted 9070 of brides and 3070 of grooms, the 1980 figures were 15°70 of brides and 4070 of grooms. The modal class of the distribution for men was shifted to younger ages (25-29 years in 1955 and 20-24 years in 1980), while it did not change for women (20-24 years). The correlation coefficient between ages of grooms and brides was 0" 81 in 1955 and 0" 88 in 1980, the relationship giving a good fit to the regression line (see table 6). Early marriages were contracted mostly between the coevals (in 1955 in early marriages brides on average
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Tab
le 6
. B
asic
sta
tist
ical
par
amet
ers
of
age
dis
trib
uti
on
s o
f sp
ou
ses
mar
ried
in
1955
an
d 1
980.
Reg
resi
on
D
ate
of
mar
riag
e M
_+ S
E
tr
"Yl +
SE
3'
2 -+
SE
r_
+ S
E
line
n
1955
G
roo
ms
(XI)
28.0
1 +
0.1
5
8"83
2
.14
+0
.04
8
.20
+0
-09
0
-80
7 +
0-0
10
Bri
des
(Yl
26
.37
+ 0
.13
7-
66
1" 7
5 +
0" 0
4 6"
76
+ 0-
09
1980
G
roo
ms
(x2)
3
0.5
2 +
0-
25
12- 5
0 1
.80
+ 0
.05
6-
21
+ 0
.10
O
. 883
+ 0
" 00
9
Bri
des
0'2)
2
7.9
6+
0-2
2
11-2
2 1-
71 +
0-0
5
5.6
9+
0.1
0
Sig
nifi
canc
e o
f di
ffer
ence
: t d
F
t d
t d
t d
x 1 -
x 2
8
.61
" 2
.00
*
5-26
* 1
5.4
0"
5.5
4*
Yl -
Y2
6
.22
*
2- 1
5"
0-6
2
8.2
8*
y =
6.7
6 +
0"
70x
3270
y=
3
.77
+0
-79
x
2564
M =
mea
n a
ge a
t m
arri
age;
o=
sta
nd
ard
dev
iati
on
; 3"
1 = c
oeff
icie
nt o
f sk
ewn
ess;
3"2
= c
oeff
icie
nt o
f k
urt
osi
s; S
E =
sta
nd
ard
er
ror;
r=
co
rrel
atio
n c
oeff
icie
nt
bet
wee
n m
ates
for
age
at
mar
riag
e; n
= n
um
ber
of
mar
ried
cou
ples
; t a
= S
tud
ent'
s te
st;
F=
Fis
her
's t
est;
* =
p <
0"
001
lev
el o
f si
gnif
ican
ce.
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Genetic demography of the Moscow population 39
were even older than grooms), but in later marriages the bride's age gradually declined in comparison with the groom's age. In 1980 the number of unions with brides older than grooms had diminished, but the number of couples in which the husband was more than 10 years older than his wife increased. According to the statistical data from the second half of the nineteenth and beginning of the twentieth centuries (Rashin 1956), in the European part of Russia, especially in rural areas, early marriages were more common. In 1910 in Moscow and Petersburg 35% of brides and 110/0 of grooms were younger than 20 years and the mean age at marriage was 24.28 + 0.03 years (a= 7-23) for women and 27.59+ 0.03 (a= 7"67) for men (calculated according to Rashin 1956). The value of the correlation coefficient between spouses, r = 0" 8, and the mean age difference of 2-3 years was typical for populations of different types (Spuhler 1968, CavaUi-Sforza and Bodmer 1971, Susanne 1979, Zhirnova 1980). Such relationships have a favourable impact on reproduction, and may lead to secondary assortative mating for phenotypic characters showing a pronounced secular trend (Cavalli-Sforza and Bodmer 1971).
Nationality. Before the Revolution mixed (interethnic) marriages in Central Russia were rare. So, even in 1925, 99" 1% of unions contracted by men of Russian nationality living in the European part of the RSFSR were within the same ethnic group (Bromley 1983). During the period from 1918 to 1933 the proportion of interethnic marriages in Moscow doubled by comparison with the pre-revolutionary rate. This was a result both of overcoming religious and ethnocultural barriers and changes in marriage legislation (Ignatyev and Prokofyeva 1936). However, even in 1955 and 1980, marked positive assortative mating for nationality is revealed in Moscow (table 7). The indices measuring the preference of intraethnic (between people of the same nationality) marriage are positive and high for all nationalities considered except Russians; the highest values are found for Jews, Tatars and Armenians. For the two latter ~roups the indices dropped substantially over the 25-year period. These indices have the important drawback that their value depends on the proportional size of the group. More plausible values expressed as a proportion of the maximum index attainable for a given ethnic group (see Coleman 1982) are presented in the last column of table 7. Now it becomes obvious that the highest values are characteristic of Jews, Tatars and Armenians, intermediate--of Russians, and the lowest--of Ukranians and Byelorussians. The proportion of interethnic marriage increased from 14.75 0/0 in 1955 to 16-53°7o in 1980 but has not yet reached the value expected under random mating.
Birthplace. Even in the late nineteenth century the radius of the marriage circle in the rural population of Moscow gubernia was still 10km: 900/0 of marriages were contracted between people born in one village or in neighbouring villages (Zhomova 1965). Today Moscow is characterized by a quite different mating pattern: unions between people both born in the capital constituted only 10% in 1955 and 38% in 1980 (figure 3). Other marriages were contracted between the Moscow-born and migrants (28o70 in 1955 and 43°70 in 1980) or between the migrants themselves (62o70 in 1955 and 19o7o in 1980). The increase in the proportion of marriages between the Muscovites and the respective decrease in the proportion of marriages between the migrants over the 25-year period resulted from the above-mentioned administrative controls on migration that became more strict. The proportion of marriages between Muscovites and migrants increased because marital migration is not regulated by administrative measures. In order to estimate the degree of assortative mating with respect to
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Tab
le 7
. M
osc
ow
eth
nic
-mat
ing
-ty
pe
freq
uen
cies
in
1955
an
d 1
980.
Hu
sban
ds
by
nat
ion
alit
y
To
tal
1 2
3 4
5 6
7 w
ives
A
A
' (°7
0)
1955
W
ives
by
nat
ion
alit
y
1 26
05
111
44
49
10
14
65
2898
+
0
.04
38
" 7
2 48
8
2 4
0 0
1 63
+
2
-30
9
-2
p~
3 27
1
4 0
0 0
1 33
+
6-
53
10.7
4
18
2 0
39
0 2
1 62
+
2
0.1
9
61
.8
5 16
0
1 0
23
0 7
47
+
44
.58
67
-2
6 1
0 0
1 0
4 0
6 +
104
.57
66"5
7
33
0 0
1 1
0 23
58
+
11
.81
--
Tot
al h
usb
and
s 27
48
122
51
94
34
20
98
3167
1980
W
ives
by
nat
ion
alit
y
h'l
1 18
94
76
19
29
24
18
46
2106
+
0
.03
2
6.9
•
2 41
4
0 2
2 0
3 52
+
1.
12
4.2
3
13
0 1
0 0
0 0
14
+
7.3
6
6.3
4
11
2 0
19
0 0
1 33
+
24
-43
56"6
~:
~ 5
26
1 0
0 22
0
4 53
+
18
.83
43
.6
~,~"
6 13
1
0 1
0 5
0 20
+
2
3.3
8
24
.2
~.
7 46
1
0 2
1 1
12
63
+
5"76
--
~
J
Tot
al h
usb
and
s 20
44
85
20
53
49
24
66
2341
Co
nti
ng
ency
coe
ffic
ient
: 19
55:
K=
O" 3
7 X
2 =
25
93*
d.f
. =
36
1980
: K
= O
" 28
X 2 =
108
4"
d.f
. =
36
Nat
ion
alit
y o
f th
e sp
ou
ses:
1 =
Ru
ssia
ns,
2 =
Uk
rain
ian
s, 3
= B
yel
oru
ssia
ns,
4 =
Jew
s, 5
= T
atar
s, 6
= A
rmen
ian
s, 7
= o
ther
s; A
= i
ndex
of
asso
rtat
ive
mat
ing
in
the
mai
n d
iag
on
al,
esti
mat
ing
th
e ex
cess
of
mar
riag
es b
etw
een
peo
ple
of
the
sam
e na
tion
alit
y: A
= (
NO
- N
E)/
NE
, w
her
e N
O =
ob
serv
ed n
um
ber
of
coup
les
wit
h gi
ven
com
bin
atio
n o
f na
tion
alit
ies,
NE
= n
um
ber
exp
ecte
d u
nd
er r
and
om
mat
ing
, A
' =
ind
ex o
f as
sort
ativ
e m
atin
g e
xp
ress
ed a
s a
pro
po
rtio
n o
f th
e m
axim
um
A a
ttai
nab
le f
or
give
n n
atio
nal
ity
.
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REGION, Na
Genetic demographyoftheMoscowpopulation
~955
41
REGION, Nn
'1980
Figure 3. 'Marriage circle' of the Moscow population in 1955 and in 1980. In the centre, percentage share of marriages between Moscow-born people. Figures inside each circumference denote percentages of marriages between Moscow-borns and, respectively, brides and grooms born in different regions of the USSR plotted and numbered according to their distance from Moscow in the same way as in figures 1 and 2 and in table 3. Percentage share of marriages between the migrants from all these regions is given in light
ellipses. The upper part of the figure refers to 1955, the lower part to 1980.
birthplace, husband-wife migration matrices have been constructed for those joined in marriage in 1955 and 1980, where birthplaces are grouped into large regions in the same way as in table 3. (For details of these matrices see Kurbatova and Pobedonostseva 1988a). The deviation from random mating appeared to be quite pronounced for this character as well: contingency coefficient K equalled 0-16 for the 1955 matrix and 0.11 for 1980. In both cases the predominance of the diagonal elements of the matrix is obvious, resulting from the fact that Moscow-born individuals marry each other more often than is expected under random mating. This finding also applies to persons born in many other regions of the USSR: they give mating preference to their country-men and -women, even when the marriage is contracted in Moscow. Because of such assortment, and given the substantial number of marriages between migrants (especially in 1955), the mean distance between birthplaces of husband and wife may not be twice as long as parent-offspring distance presented in table 4 (as predicted from an ideal model). In the extreme case of complete positive assortative mating the distance between the birthplaces of spouses would be zero, regardless of their independent migration to Moscow from distant regions. This second variant of isolation by distance model, based on marital distances, was calculated separately for
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42 D.L. Kurbatova and E. Yu. Pobedonostseva
spouses of Russian nationality (table 8). When measuring the distance between birthplaces of husband and wife, we took distances between administrative centres of the respective provinces. Comparison of the basic parameters of the two models (tables 4 and 8) shows that the mean marital distance slightly exceeds the mean parent-offspring distance and confirms the increase in long-range migration and the reduction of short-range migration. The degree of isolation by distance calculated by this method is also quite small, suggesting weak dependence of genetic kinship on distance for spouses of Russian nationality (given that the Moscow-type mating pattern is widespread). In 1980 the mean marital distance significantly exceeded that in 1955, mainly because of the increase in marital distance in marriages between migrants. Indeed, in 1955, 245 intraprovince marriages have been encountered in the studied marriage cohort (not counting unions between Moscow-born and those between people born in Moscow and Moscow province). Such marriages, characterized by marital distance of 0-100km, are especially numerous between the natives of Central region (Ryazan, Moscow, Tula and Kaluga provinces) and constitute 9-4070 of all marriages between Russians in 1955. In the 1980 cohort these marriages were few--37 (1 "9070). It is noteworthy that in 'mixed' (interethnic) marriages both in 1955 and in 1980 mean marital distance is roughly twice as large as in marriages between Russians. The smallest marital distance was found in intraethnic unions between people of nationalities other than Russian. A large proportion of such marriages was contracted between people born in one village, one town or one province. Therefore assortative mating for birthplace could be at least in part ascribed to the effect of ethnic endogamy. In this connection, at the current stage of Moscow population development only intraethnic marriages between people of non-Russian nationality could be considered a possible cohort for the expression of inbreeding effects.
Profession. In pre-revolutionary Russia marriages were contracted mainly within social groups. Nowadays it seems appropriate to estimate the degree of assortative
Table 8. Basic parameters of the model of isolation by distance in the Moscow population from data on marital distances of couples of Russian nationality.
Date of marriage a s m s ' k m e b
1955 0.0113 0.4334 503 +_ 14 893 611 0- 0996 0.0007
(n = 2607) d i> 2500 43 < d i < 2500
1980 0"0162 0.2675 646+29 1416 937 0-0945 0.0005
(n= 1918) d i > 4005 66 < di<4005
m=½P (di>4s,,/2), the long-range migration rate; s ' = the central standard deviation for short-range migration (d i< 4s,~); k= ½P 4s~<di<s/(lOx/2), the short-range migration rate; n = number of married couples; for other definitions, see table 4.
Table 9. Estimates of the degree of assortative mating for four characters.
Date of Nationality Birthplace Profession marriage Age d.f. = 36 d.f. = 256 d.f. = 121
1 9 5 5 r = 0 . 8 0 7 + 0 . 0 1 0 K =0-37 K =0 .16 K =0 .27 X 2 = 2593* X 2 = 1296" X 2 = 2715"
1980 r = 0 . 8 8 3 + 0 . 0 0 9 K =0 .28 K =0.11 K =0"32 X 2 = 1084" X 2 = 479* X 2 = 2851"
r = Correlation coefficient; K = contingency coefficient; * = p < 0.001 level of significance.
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Genetic demography o f the Moscow population 43
mating with respect to professions. For simplicity these were grouped into the following categories: 1, production workers; 2, employers in the service sector; 3, engineers and technicians; 4, economists, accountants; 5, physicians and medical staff; 6, teachers, librarians, lawyers; 7, scientists and artists; 8, administrative personnel; 9, military staff; 10, students; 11, pensioners; 12, others. Analysis of the corresponding matrices (see Kurbatova and Pobedonostseva 1988b) revealed a substantial deviation from panmixia: K = 0.27 in 1955 and K = 0.32 in 1980 (table 9). Positive indices of assortative mating, demonstrating preferential mating among individuals of related professions, are characteristic of all 12 professional groups considered, the indices being especially high for categories 5-7 and 10.
4. Discussion It is evident that the process of urbanization, involving to a certain extent all
populations in the USSR, leads more or less uniformly to a transition from isolation and inbreeding to the alternative state of outbreeding. The intensity of outbreeding in Moscow is characterized by the proportion of interethnic marriage (16-5%) and by marital distance (650 km); the latter is large in comparison with known data on urban populations in the West (Coleman 1982). Many recently established and rapidly developing towns in Siberia, the Far East and other regions with industrial projects conform to this new model of population structure to an even greater extent than Moscow (see Bochkov, Nikolaeva, Tikhopoy, Lunga and Prusakov 1984). For instance, according to migration statistics data (Tatevosyan 1972), the mean distance travelled by migrants arriving in urban centres in the Soviet Far East equals 3865 km, while for those arriving in towns and cities of the Central region this distance averages 1069 km (the latter value is practically equal to that obtained in the present paper for migrants arriving in Moscow). Some multinational populations of the USSR have a greater proportion of interethnic marriage than has Moscow: in the Middle-Asian large cities inter-racial unions are rather frequent (see Svyatova, Kuandikov and Chulkina 1988). The genetic processes accompanying outbreeding have not yet been completely established; however, a possible increase in recombination rates has been predicted, thus suggesting the need for an adequate monitoring model capable of following the dynamics of genetic load and other valuable population parameters (Altukhov and Kurbatova 1984).
The results of the preceding analysis show that the Moscow population gene pool, being related by origin and during many centuries to the populations of indigenous Russian 'gubernias', should at the present time include genetic information drawn from all ethnic and geographical components of migration flow. Given this high migration intensity, in combination with a reduction in the compactness of each ethnic group's settlements, the populations of the largest cities in the USSR could achieve the state of complete panmixia were it not for the counteracting effect of positive assortative mating. Summarizing all the data considered above, we can estimate the effectiveness of this counteracting factor in the following terms: assortative mating for ethnic characters reduces the expected magnitude of outbreeding by 28% in 1955 and by 20% in 1980; deviation from random mating with respect to birthplace diminishes the effective migration value by 10% in 1955 and by 20% in 1980.
During the study period (1955-80) assortative mating for nationality and birthplace tended to decline while that for age and profession increased (table 9). Preferential intraethnic marriage is characteristic not only of Moscow, but has also been demonstrated for Angarsk (Bochkov et al. 1984) and Alma-Ata (Svyatova et al. 1988).
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44 D.L. Kurbatova and E. Yu. Pobedonostseva
The present paper does not aim to reveal factors causing assortative mating in the modern cities of the USSR. It is evident that explanations for these factors are mainly to be found in the field of social psychology (Eckland 1968), a contention supported by the high degree of assortative mating for profession observed in this study. Soviet ethnologists name several factors determining the citizen's attitude to a 'mixed' marriage: predominant language of communication, the extent of social activity, the intensity of social contacts with persons from a different ethnic environment at work or in everyday life, age and educational level. Representatives of dispersed ethnic groups inhabiting the polyethnic environment of a large city often choose mates in localities from which they have arrived in the past (Shkaratan 1986; Susokolov 1987). As we have already mentioned, in a large population mating choice for ethnic and socio- demographic parameters can cause secondary assortative mating for related phenotypic traits with pronounced heritability. Consequently, the genetic sequelae of positive assortative mating may be similar to inbreeding effects in populations of small size: an increase in the additive component of variance of quantitative traits, and greater frequency of rare recessive phenotypes (Cavalli-Sforza and Bodmer 1971). In addition, assortative mating, by contribution to social stratification and narrowing of mate choice, might be attended by selective mating. The fact that almost 20% of Moscow women of completed fertility have left no genetic contribution to the next generation may in part be attributed to the difficulties of mating choice (Kucher and Kurbatova 1986).
Thus, we can conclude that assortative mating, along with migration, plays a substantial role in governing the Moscow population gene pool and a high immigration coefficient in itself cannot measure the amount of outbreeding. Whereas migration pressure tends to increase genetic variation of an urban population, positive assortative mating acts to prevent the amalgamation of this variation in a common gene pool.
References ALTUKHOV, YU. P., and KURBATOVA, O.L., 1984, Human heredity and environment (in Russian). In
Human Heredity and Environment, edited by Yu. P. ALTtJKHOV (Moscow: Nauka), pp. 7-35. BOCHKOV, N.P., NIKOLAEVA, I.V., TIKHOPOY, M.V., LUNGA, I.N., and PRUSAKOV, V.M., 1984,
Assortative mating in contemporary urban population. Soviet Genetics. Translated from Russian: Genetika, 20, 1224-1229.
BROMLEY, YU. V., 1983. An Essay on the Theory of Ethnos (in Russian). (Moscow: Nauka). CAVALLI-SFORZA, L. L., and BOOMER, W.F., 1971. The Genetics of Human Populations (San Francisco:
Freeman & Co.). COLEMAN, D., 1982. The population structure of urban area in Britain. In Current Developments in
A nthropological Genetics, Vol. 2: Ecological and Population Structure, edited by M. H. Crawford and J. H. Mielke (University of Kansas, Lawrence, Kansas; New York; London: Plenum Press), pp. 467-506.
ECKLAr~D, B. K., 1968, Theories of mate selection. Eugenics Quarterly, 15, 71-84. FEnoTovsKAYA, G., 1980, The regulation of population growth--Moscow experiment (in Russian). In On
Moscow Population, edited by D. I. Valentey (Moscow: Statistika), pp. 52-63. IGNATYEV, M.V., and PIZOKOFVEVA, T.I., 1936, Data on inbreeding in the Moscow population (in
Russian), In Transactions of the Medico-Genetical Institute, Vol.4 (Moscow-Leningrad: Biomedgiz), pp. 201-212.
KHOREV, B. S., and KlSELEVA, G. P., 1982, Urbanization and the Demographic Process (Moscow: Finansi i Statistica).
KUCHER, A.N., and KURBATOVA, O.L., 1986, The population-genetics study of differential fertility in urban population. Soviet Genetics, translated from Russian: Genetika, 22, 304-311.
KURBATOVA, O.L., 1975, An attempt of genetic-demographic study of large panmictic populations (in Russian). Voprosy Antropologii, 50, 30-45.
KURBATOVA, O. L., and POBEDONOSTSEVA, E. Yu., 1988a, Role of migration in forming marriage structure of the Moscow population, 2. Soviet Genetics, translated from Russian: Genetika, 24, 1679-1688.
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Genetic demography o f the M o s c o w populat ion 45
KURBATOVA, O. L., and POBEDONOSTSEVA, E. Yu., 1988b, Role of migration in forming marriage structure of the Moscow population. 3. Soviet Genetics, translated from Russian: Genetika, 24, 1689-1695.
KURBATOVA, O. L., and RYCHCOV, Yu. G., 1978. The most important peculiarities of the genetic process in urban population. In 14th International Genetic Congress. Abstracts of contributed papers. Sessions, part 2 (Moscow: Nauka), p. 403.
KURBATOVA, O.L., POBEDONOSTSEVA, E. Yu., and IMASHEVA, A.G., 1984a, Reflection of some demographic trends in the genetic structure of the Moscow population. In Abstracts of the International Conference on Project 12 of the UNESCO Programme on Man and Biosphere (Moscow: Institute of General Genetics), pp. 180-183.
KURBATOVA, O. L., POBEDONOSTSEVA, E. YU., and IMASHEVA, A.G., 1984b, Role of migration in forming marriage structure of the Moscow population. 1. Soviet Genetics, translated from Russian: Genetika, 20, 394-402.
LAKIN, G.F., 1980, Biometry (in Russian), (Moscow: Vysshaya Shkola). MORTON, N.E., 1977, Isolation by distance in human populations. Annals of Human Genetics, 40,
361-365. NIFONTOV, A.S., 1954, Population of capitalistic Moscow (in Russian). In The History of Moscow, Vol. 4
(Moscow: Academia Nauk SSSR), p. 231. RABINOVICH, M. G., 1978. An Essay on the Ethnography of Russian Feudal City (in Russian). (Moscow:
Nauka). RASHIN, A.G. , 1956. The Population of Russia during 100 Years (in Russian). (Moscow: Gosstatizdat). RYcncov, Yu. G., 1979. Comparative study of the genetic process in urbanized and isolated populations
(in Russian). Voprosy Antropologii, 63, 3-21. SHKARATAN, O. J., (ed.), 1986), Ethnosocial Problems of the City, (in Russian). (Moscow: Nauka). SPUHLER, J. N., 1968. Assortative mating with respect to physical characteristics. Eugenics Quarterly, 15,
128-140. SUSANNE, C., 1979. Assortative mating: biodemographical structure of human populations. Journal of
Human Evolution, 8, 799-804. SUSOKOLOV, A.A., 1987, International Marriages in the USSR (in Russian). (Moscow: Mysl). SVYATOVA, G. S., KUANDIKOV, Ye. U., and CHULKINA, M.P. , 1988, Genetic-demographic characteristics
of the population of the large multinational city (on the basis of Alma-Ata). Soviet Genetics, translated from Russian. Genetika, 24, 1269-1275.
TATEVOSYAN, R.V., 1972, Methods of analysis of interregional migration in the USSR in relation to the process of urbanization. Soviet Geography, 13, 126-131.
VYDRO, M. Ya., 1976, The Moscow Population (in Russian). (Moscow: Statistica). ZHIRNOVA, G. V., 1980. Marriage and Wedding of Russian Citizens in the Past and at Present (in Russian).
(Moscow: Nauka). ZHOMOVA, V.K., 1965, Data on marital distance in Russian population (in Russian). Voprosy
Anthropologii, 21, 111-114.
Address for correspondence: O,K, Kurbatova, N.I. Vavilov Institute of General Genetics, USSR Academy of Sciences, Gubkin St. 3, Moscow B-333, 117809 GSP-1, USSR.
Zusammenfassnng. Unter Verwendung von Heiratsurkunden, Zensusdaten und anderen statistischen Quellen wurden einige demographische Parameter der Moskauer Bev61kerung in den Jahren 1955 und 1980 analysiert, wie z.B. Heiratsalter, Geburtsort, Nationalit~it und Beruf. Es konnte gezeigt werden, dab Migration der wesentlichste Faktor for die Moskauer Populationsdynamik ist. Genetisch bedeutsame quantitative und geographische Parameter dieses Prozesses wurden herausgearbeitet (Migrationsraten, Migrations- und Heiratsdistanzen, Anteil interethnischer Heiraten). In den letzten zwei Jahrhunderten ist die durchschnittliche Herkunftsentfernung der Zuwanderer nach Moskau um ein Mehrfaches gestiegen, wobei der genetische Beitrag der 6stlichen und stidlichen Landesteile besonders ausgepragt ist. In der Periode maximaler Migrationsraten betrug der prozentuale Anteil an Heiraten zwischen Partnern, die beide in Moskau geboren waren, lediglich 10°70. Der prozentuale Anteil interethnischer Heiraten betrug 1955 14,75% und 1980 16,53070. Der Grad der isolation by distance, der sich aus Mal&ots Modell ergibt, erschien ziemlich gering. Ein positives assortative mating hinsichtlich Nationalit~it, Geburtsort, Alter und Beruf wurde als Faktor charakterisiert, der dem Outbreeding entgegenwirkt. W~ihrend die sch~dlichen Effekte yon Isolation und Inbreeding hinreichend bekannt sind, sind die genetischen Konsequenzen des alternativen Zustands noch unbekannt.
R6sum& A partir des registres de mariage, des recensements et d'autres sources statistiques, on a 6tudi6 certains param6tres d6mographiques de la population de Moscou en 1955 et 1980, tels que t'~ge au mariage, le lieu de naissance, la nationalit6 et la profession des r6sidents permanents. La migration apparait &re le principal facteur dynamique de la population moscovite. Des param~tres quantitatifs g6n6tiques et g6ographiques de ce processus ont 6t6 obtenus (taux de migration, migration et distance maritale, proportion des mariages interethniques). Au cours des deux derniers si~cles, la distance moyenne par-
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46 D.L. Kurbatova and E. Yu. Pobedonostseva
courue par les migrants arrivant a Moscou s'est accrue ~ plusieurs reprises, les contributions g6n6tiques des r6gions sud et est du pays ~tant particuli~rement marqu6es. Pendent la p6riode des taux de migration maximum, la part des mariages entre personnes natives de Moscou 6tait seulement de 10% de la totalit6 des mariages. La part des mariages interethniques ~tait de 14,75°70 en 1955 et de 16,53o70 en 1980. Le degr6 d'isolement par la distance pr6vu par le module de Mal6cot, apparait tr~s bas. L'assortiment matrimonial positif pour la nationalit6, le lieu de naissance, l',~ge et la profession, constitue un facteur oppos6 l'ouverture des mariages. Alors que l'effet d616t&e de l'iosolement et de la consanguinit6 sont bien connus, les consequences g~n&iques de l'~tat inverse sont encore obscures.
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