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How We Do It

The evolution and future of human reproduction

Miscarriage
Why Too Many Sperms Spoil the Egg

Robert D. Martin Ph.D. on August 11, 2017

Men can produce too many sperms as well as too few. Excessive sperm numbers around an egg can result in multiple fertilization, abnormal chromosome numbers, and miscarriage.

Men can produce too many sperms as well as too few. Excessive sperm numbers around an egg can result in multiple fertilization, abnormal chromosome numbers, and miscarriage.

Understanding Twins
Twins and More: Too Much of a Good Thing?

Robert D. Martin Ph.D. on July 25, 2017

Multiple pregnancies bring more bundles of joy, but premature birth is more common. Delayed motherhood and fertility treatments are boosting the frequency of multiple births.

Multiple pregnancies bring more bundles of joy, but premature birth is more common. Delayed motherhood and fertility treatments are boosting the frequency of multiple births.

Understanding Twins
Twins With Two Daddies

Robert D. Martin Ph.D. on June 22, 2017

Paternity suits triggered by strikingly different fraternal twins have revealed bizarre cases with two different fathers. Split paternity is the visible tip of a sizeable iceberg.

Paternity suits triggered by strikingly different fraternal twins have revealed bizarre cases with two different fathers. Split paternity is the visible tip of a sizeable iceberg.

Health
The Rising Tide of Caesarean Births

Robert D. Martin Ph.D. on May 18, 2017

C-sections have been multiplying out of control worldwide. Evidence for side-effects has mounted in tandem, but in the USA at least it seems that the tide may have turned.

C-sections have been multiplying out of control worldwide. Evidence for side-effects has mounted in tandem, but in the USA at least it seems that the tide may have turned.

Health
Going, Going, Gone? Human Sperm Counts Are Plunging

Robert D. Martin Ph.D. on April 20, 2017

Accumulated evidence confirms that human sperm counts have fallen markedly in industrialized countries since the 1930s. Male fertility and reproductive health are threatened.

Accumulated evidence confirms that human sperm counts have fallen markedly in industrialized countries since the 1930s. Male fertility and reproductive health are threatened.

Pregnancy
The Benefits of Breastfeeding...for Mothers

Robert D. Martin Ph.D. on March 14, 2017

Breast-feeding benefits mothers, not just babies. It speeds recovery of the womb after birth. Later in life, risks of heart disease and breast and ovarian cancer are reduced.

Breast-feeding benefits mothers, not just babies. It speeds recovery of the womb after birth. Later in life, risks of heart disease and breast and ovarian cancer are reduced.

Sex
St. Valentine’s Day and the Biology of Romantic Kissing

Robert D. Martin Ph.D. on February 14, 2017

For Westerners, kisses and Valentine’s Day are inseparable. But new cross-cultural evidence challenges evolutionary inferences regarding possible biological functions of kissing.

For Westerners, kisses and Valentine’s Day are inseparable. But new cross-cultural evidence challenges evolutionary inferences regarding possible biological functions of kissing.

Hormones
Coping With Hormonal Ups and Downs

Robert D. Martin Ph.D. on October 17, 2016

Major hormonal changes across the menstrual cycle may influence a woman’s mood, well-being and performance. But apart from PMS side-effects are milder than often thought.

Major hormonal changes across the menstrual cycle may influence a woman’s mood, well-being and performance. But apart from PMS side-effects are milder than often thought.

Miscarriage
A Downside for Trophy Wives: Sexually Diminished Husbands

Robert D. Martin Ph.D. on August 9, 2016

Increasing reproductive problems with age are by no means confined to women. Clear evidence of similar drawbacks for men has been widely ignored. Trophy wives pay a high price!

Increasing reproductive problems with age are by no means confined to women. Clear evidence of similar drawbacks for men has been widely ignored. Trophy wives pay a high price!

Adolescence
Unmanned: An Unnatural History of Human Castration

Robert D. Martin Ph.D. on July 14, 2016

Deliberate castration, long used to punish criminals and prisoners of war, has also yielded harem guards and has been inflicted on young boys to stop their voices from breaking.

Deliberate castration, long used to punish criminals and prisoners of war, has also yielded harem guards and has been inflicted on young boys to stop their voices from breaking.

Depression
Honey, I Squished the Kids’ Heads!

Robert D. Martin Ph.D. on June 13, 2016

Around the world, people have tightly bound their babies’ heads to produce distinctive shapes. Extreme cases in South America have spawned wild stories of intervention by aliens.

Around the world, people have tightly bound their babies’ heads to produce distinctive shapes. Extreme cases in South America have spawned wild stories of intervention by aliens.

Sex
Summertime Sex and Springtime Babies

Robert D. Martin Ph.D. on May 10, 2016

Human populations have regular year-round birth patterns. Births typically peak in spring in the north but 6 months later in the south, hinting at control by an internal clock.

Human populations have regular year-round birth patterns. Births typically peak in spring in the north but 6 months later in the south, hinting at control by an internal clock.

Pregnancy
Beating the Biological Clock with Eggs in the Freezer

Robert D. Martin Ph.D. on April 11, 2016

A widespread tendency to delay pregnancy clashes with reduced fertility and increased risks later in life. Will deep-freezing eggs of young women for later use solve the problems?

A widespread tendency to delay pregnancy clashes with reduced fertility and increased risks later in life. Will deep-freezing eggs of young women for later use solve the problems?

Pregnancy
A Biological Function for Oral Sex?

Robert D. Martin Ph.D. on February 2, 2016

High blood pressure affects 10% of pregnancies in which a mother’s immune system over-reacts to the fetus. Long-term sexual priming by a specific male partner reduces the risk.

High blood pressure affects 10% of pregnancies in which a mother’s immune system over-reacts to the fetus. Long-term sexual priming by a specific male partner reduces the risk.

Genetics
The Ripley Effect: Alien Intruders in the Womb

Robert D. Martin Ph.D. on January 5, 2016

A fetus in its mother’s womb must somehow evade detection by her immune system. In an "Alien"-like scenario, genes that permit this have been captured from once harmful viruses.

A fetus in its mother’s womb must somehow evade detection by her immune system. In an "Alien"-like scenario, genes that permit this have been captured from once harmful viruses.