22.1: Case Study: Making Babies - Biology

22.1:  Case Study: Making Babies - Biology

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Case Study: Trying to Conceive

Isabella, 28, and Omar, 30, have been together for three years. At first, they did not pay attention to the timing of their sexual activity in relation to Isabella’s menstrual cycle, but after six months passed without Isabella becoming pregnant, they decided to try to maximize their efforts.

Figure (PageIndex{1}): Couples holding hands

They knew that in order for a woman to become pregnant, the man’s sperm must encounter the woman’s egg, which is typically released once a month through a process called ovulation. They had also heard that for the average woman, ovulation occurs around day 14 of the menstrual cycle. To maximize their chances of conception, they tried to have sexual intercourse on day 14 of Isabella’s menstrual cycle each month.

After several months of trying this method, Isabella is still not pregnant. She is concerned that she may not be ovulating on a regular basis because her menstrual cycles are irregular and often longer than the average 28 days. Omar is also concerned about his own fertility. He had some injuries to his testicles (testes) when he was younger, and wonders if that may have caused a problem with his sperm.

Isabella calls her doctor for advice. Dr. Bashir recommends that she try taking her temperature each morning before she gets out of bed. This temperature is called basal body temperature (BBT), and recording BBT throughout a woman’s menstrual cycle can sometimes help identify if and when they ovulate. Additionally, Dr. Bashir recommends she try using a home ovulation predictor kit, which predicts ovulation by measuring the level of luteinizing hormone (LH) in the urine. In the meantime, Dr. Bashir sets up an appointment for Omar to give a semen sample, so that his sperm may be examined with a microscope.

As you read this chapter, you will learn about the male and female reproductive systems, how sperm and eggs are produced, and how they meet each other to ultimately produce a baby. You will learn how these complex processes are regulated, and how they can be susceptible to problems along the way. Problems in either the male or female reproductive systems can result in infertility, or difficulty in achieving a successful pregnancy. As you read the chapter, you will understand exactly how BBT and LH relate to ovulation, why Dr. Bashir recommended that Isabella monitor these variables, and the types of problems she will look for in Omar’s semen. At the end of the chapter, you will find out the results of Isabella and Omar’s fertility assessments, steps they can take to increase their chances of conception, and whether they are ultimately able to get pregnant.


Most of the information in this chapter is in terms of cis-gendered individuals because there is a lack of data on lesbian, gay, bisexual, transgender, and queer (LGBTQ) individuals. About 3.5% of Americans identify themselves as lesbian, gay, or bisexual, and 0.3% identify themselves as transgender. The acronym LGBTQIA+ is an umbrella term that includes a number of groups: lesbian (homosexual woman), gay (homosexual man or woman), bisexual (person who is attracted to both genders), transgender (person who identifies their gender as different from their biological one), queer (a synonym for gay; some people prefer to identify themselves as queer to empower themselves and take their identity “back from the bullies”), questioning (people who are unsure about their gender identity/sexuality), intersex (people with two sets of genitalia), asexual (people who are not sexually attracted to anyone and who don’t identify with any orientation), allies (the loving supporters of the community, though not necessarily part of it), two spirits (a tradition in many First Nations that considers sexual minorities to have both male and female spirits), and pansexual (person sexually attracted to others of any sex or gender).

Chapter Overview: Reproductive System

In this chapter, you will learn about the male and female reproductive systems. Specifically, you will learn about:

  • The functions of the reproductive system, which include the production and fertilization of gametes (eggs and sperm), the production of sex hormones by the gonads (testes and ovaries), and, in females, the carrying of a fetus
  • How the male and female reproductive systems differentiate in the embryo and fetus, and how they mature during puberty
  • The structures of the male reproductive system, including the testes, epididymis, vas deferens, ejaculatory ducts, seminal vesicles, prostate gland, bulbourethral glands, and the penis
  • How sperm are produced, matured, stored, and deposited into the female
  • The fluids in semen that protect and nourish sperm, and where those fluids are produced
  • Disorders of the male reproductive system, including erectile dysfunction, epididymitis, prostate cancer, and testicular cancer—some of which predominantly affect younger men
  • The structures of the female reproductive system, including the ovaries, fallopian tubes, uterus, cervix, vagina, and external structures of the vulva
  • How eggs are produced in the female fetus, and how they then mature after puberty through the process of ovulation
  • The menstrual cycle, its purpose, and the hormones that control it
  • How fertilization and implantation occur, the stages of pregnancy and childbirth, and how the mother’s body produces milk to feed the baby
  • Disorders of the female reproductive system, including cervical cancer, endometriosis, and vaginitis (which includes yeast infections)
  • Some causes and treatments of male and female infertility
  • Forms of contraception (birth control), including barrier methods (such as condoms), hormonal methods (such as the birth control pill), behavioral methods, intrauterine devices, and sterilization

As you read the chapter, think about the following questions:

  1. Why might sexual intercourse on day 14 of Isabella's menstrual cycle not necessarily be optimal timing to achieve a pregnancy?
  2. Why is Isabella concerned about her irregular and long menstrual cycles? How could tracking her BBT and LH level help identify if she is ovulating and when?
  3. Why do you think Omar is concerned about past injuries to his testes? How might an analysis of his semen help assess whether he has a fertility issue—and, if so, the type of issue?

1.1 The Science of Biology

By the end of this section, you will be able to do the following:

  • Identify the shared characteristics of the natural sciences
  • Summarize the steps of the scientific method
  • Compare inductive reasoning with deductive reasoning
  • Describe the goals of basic science and applied science

What is biology? In simple terms, biology is the study of life. This is a very broad definition because the scope of biology is vast. Biologists may study anything from the microscopic or submicroscopic view of a cell to ecosystems and the whole living planet (Figure 1.2). Listening to the daily news, you will quickly realize how many aspects of biology we discuss every day. For example, recent news topics include Escherichia coli (Figure 1.3) outbreaks in spinach and Salmonella contamination in peanut butter. Other subjects include efforts toward finding a cure for AIDS, Alzheimer’s disease, and cancer. On a global scale, many researchers are committed to finding ways to protect the planet, solve environmental issues, and reduce the effects of climate change. All of these diverse endeavors are related to different facets of the discipline of biology.

The Process of Science

Biology is a science, but what exactly is science? What does the study of biology share with other scientific disciplines? We can define science (from the Latin scientia, meaning “knowledge”) as knowledge that covers general truths or the operation of general laws, especially when acquired and tested by the scientific method. It becomes clear from this definition that applying scientific method plays a major role in science. The scientific method is a method of research with defined steps that include experiments and careful observation.

We will examine scientific method steps in detail later, but one of the most important aspects of this method is the testing of hypotheses by means of repeatable experiments. A hypothesis is a suggested explanation for an event, which one can test. Although using the scientific method is inherent to science, it is inadequate in determining what science is. This is because it is relatively easy to apply the scientific method to disciplines such as physics and chemistry, but when it comes to disciplines like archaeology, psychology, and geology, the scientific method becomes less applicable as repeating experiments becomes more difficult.

These areas of study are still sciences, however. Consider archaeology—even though one cannot perform repeatable experiments, hypotheses may still be supported. For instance, an archaeologist can hypothesize that an ancient culture existed based on finding a piece of pottery. He or she could make further hypotheses about various characteristics of this culture, which could be correct or false through continued support or contradictions from other findings. A hypothesis may become a verified theory. A theory is a tested and confirmed explanation for observations or phenomena. Therefore, we may be better off to define science as fields of study that attempt to comprehend the nature of the universe.

Natural Sciences

What would you expect to see in a museum of natural sciences? Frogs? Plants? Dinosaur skeletons? Exhibits about how the brain functions? A planetarium? Gems and minerals? Maybe all of the above? Science includes such diverse fields as astronomy, biology, computer sciences, geology, logic, physics, chemistry, and mathematics (Figure 1.4). However, scientists consider those fields of science related to the physical world and its phenomena and processes natural sciences . Thus, a museum of natural sciences might contain any of the items listed above.

There is no complete agreement when it comes to defining what the natural sciences include, however. For some experts, the natural sciences are astronomy, biology, chemistry, earth science, and physics. Other scholars choose to divide natural sciences into life sciences , which study living things and include biology, and physical sciences , which study nonliving matter and include astronomy, geology, physics, and chemistry. Some disciplines such as biophysics and biochemistry build on both life and physical sciences and are interdisciplinary. Some refer to natural sciences as “hard science” because they rely on the use of quantitative data. Social sciences that study society and human behavior are more likely to use qualitative assessments to drive investigations and findings.

Not surprisingly, the natural science of biology has many branches or subdisciplines. Cell biologists study cell structure and function, while biologists who study anatomy investigate the structure of an entire organism. Those biologists studying physiology, however, focus on the internal functioning of an organism. Some areas of biology focus on only particular types of living things. For example, botanists explore plants, while zoologists specialize in animals.

Scientific Reasoning

One thing is common to all forms of science: an ultimate goal “to know.” Curiosity and inquiry are the driving forces for the development of science. Scientists seek to understand the world and the way it operates. To do this, they use two methods of logical thinking: inductive reasoning and deductive reasoning.

Inductive reasoning is a form of logical thinking that uses related observations to arrive at a general conclusion. This type of reasoning is common in descriptive science. A life scientist such as a biologist makes observations and records them. These data can be qualitative or quantitative, and one can supplement the raw data with drawings, pictures, photos, or videos. From many observations, the scientist can infer conclusions (inductions) based on evidence. Inductive reasoning involves formulating generalizations inferred from careful observation and analyzing a large amount of data. Brain studies provide an example. In this type of research, scientists observe many live brains while people are engaged in a specific activity, such as viewing images of food. The scientist then predicts the part of the brain that “lights up” during this activity to be the part controlling the response to the selected stimulus, in this case, images of food. Excess absorption of radioactive sugar derivatives by active areas of the brain causes the various areas to "light up". Scientists use a scanner to observe the resultant increase in radioactivity. Then, researchers can stimulate that part of the brain to see if similar responses result.

Deductive reasoning or deduction is the type of logic used in hypothesis-based science. In deductive reasoning, the pattern of thinking moves in the opposite direction as compared to inductive reasoning. Deductive reasoning is a form of logical thinking that uses a general principle or law to predict specific results. From those general principles, a scientist can deduce and predict the specific results that would be valid as long as the general principles are valid. Studies in climate change can illustrate this type of reasoning. For example, scientists may predict that if the climate becomes warmer in a particular region, then the distribution of plants and animals should change.

Both types of logical thinking are related to the two main pathways of scientific study: descriptive science and hypothesis-based science. Descriptive (or discovery) science , which is usually inductive, aims to observe, explore, and discover, while hypothesis-based science , which is usually deductive, begins with a specific question or problem and a potential answer or solution that one can test. The boundary between these two forms of study is often blurred, and most scientific endeavors combine both approaches. The fuzzy boundary becomes apparent when thinking about how easily observation can lead to specific questions. For example, a gentleman in the 1940s observed that the burr seeds that stuck to his clothes and his dog’s fur had a tiny hook structure. On closer inspection, he discovered that the burrs’ gripping device was more reliable than a zipper. He eventually experimented to find the best material that acted similarly, and produced the hook-and-loop fastener popularly known today as Velcro. Descriptive science and hypothesis-based science are in continuous dialogue.

The Scientific Method

Biologists study the living world by posing questions about it and seeking science-based responses. Known as scientific method, this approach is common to other sciences as well. The scientific method was used even in ancient times, but England’s Sir Francis Bacon (1561–1626) first documented it (Figure 1.5). He set up inductive methods for scientific inquiry. The scientific method is not used only by biologists researchers from almost all fields of study can apply it as a logical, rational problem-solving method.

The scientific process typically starts with an observation (often a problem to solve) that leads to a question. Let’s think about a simple problem that starts with an observation and apply the scientific method to solve the problem. One Monday morning, a student arrives at class and quickly discovers that the classroom is too warm. That is an observation that also describes a problem: the classroom is too warm. The student then asks a question: “Why is the classroom so warm?”

Proposing a Hypothesis

Recall that a hypothesis is a suggested explanation that one can test. To solve a problem, one can propose several hypotheses. For example, one hypothesis might be, “The classroom is warm because no one turned on the air conditioning.” However, there could be other responses to the question, and therefore one may propose other hypotheses. A second hypothesis might be, “The classroom is warm because there is a power failure, and so the air conditioning doesn’t work.”

Once one has selected a hypothesis, the student can make a prediction. A prediction is similar to a hypothesis but it typically has the format “If . . . then . . . .” For example, the prediction for the first hypothesis might be, “If the student turns on the air conditioning, then the classroom will no longer be too warm.”

Testing a Hypothesis

A valid hypothesis must be testable. It should also be falsifiable , meaning that experimental results can disprove it. Importantly, science does not claim to “prove” anything because scientific understandings are always subject to modification with further information. This step—openness to disproving ideas—is what distinguishes sciences from non-sciences. The presence of the supernatural, for instance, is neither testable nor falsifiable. To test a hypothesis, a researcher will conduct one or more experiments designed to eliminate one or more of the hypotheses. Each experiment will have one or more variables and one or more controls. A variable is any part of the experiment that can vary or change during the experiment. The control group contains every feature of the experimental group except it is not given the manipulation that the researcher hypothesizes. Therefore, if the experimental group's results differ from the control group, the difference must be due to the hypothesized manipulation, rather than some outside factor. Look for the variables and controls in the examples that follow. To test the first hypothesis, the student would find out if the air conditioning is on. If the air conditioning is turned on but does not work, there should be another reason, and the student should reject this hypothesis. To test the second hypothesis, the student could check if the lights in the classroom are functional. If so, there is no power failure and the student should reject this hypothesis. The students should test each hypothesis by carrying out appropriate experiments. Be aware that rejecting one hypothesis does not determine whether or not one can accept the other hypotheses. It simply eliminates one hypothesis that is not valid (Figure 1.6). Using the scientific method, the student rejects the hypotheses that are inconsistent with experimental data.

While this “warm classroom” example is based on observational results, other hypotheses and experiments might have clearer controls. For instance, a student might attend class on Monday and realize she had difficulty concentrating on the lecture. One observation to explain this occurrence might be, “When I eat breakfast before class, I am better able to pay attention.” The student could then design an experiment with a control to test this hypothesis.

In hypothesis-based science, researchers predict specific results from a general premise. We call this type of reasoning deductive reasoning: deduction proceeds from the general to the particular. However, the reverse of the process is also possible: sometimes, scientists reach a general conclusion from a number of specific observations. We call this type of reasoning inductive reasoning, and it proceeds from the particular to the general. Researchers often use inductive and deductive reasoning in tandem to advance scientific knowledge (Figure 1.7). In recent years a new approach of testing hypotheses has developed as a result of an exponential growth of data deposited in various databases. Using computer algorithms and statistical analyses of data in databases, a new field of so-called "data research" (also referred to as "in silico" research) provides new methods of data analyses and their interpretation. This will increase the demand for specialists in both biology and computer science, a promising career opportunity.

Visual Connection

In the example below, the scientific method is used to solve an everyday problem. Match the scientific method steps (numbered items) with the process of solving the everyday problem (lettered items). Based on the results of the experiment, is the hypothesis correct? If it is incorrect, propose some alternative hypotheses.

1. Observation a. There is something wrong with the electrical outlet.
2. Question b. If something is wrong with the outlet, my coffeemaker also won’t work when plugged into it.
3. Hypothesis (answer) c. My toaster doesn’t toast my bread.
4. Prediction d. I plug my coffee maker into the outlet.
5. Experiment e. My coffeemaker works.
6. Result f. Why doesn’t my toaster work?

Visual Connection

Decide if each of the following is an example of inductive or deductive reasoning.

  1. All flying birds and insects have wings. Birds and insects flap their wings as they move through the air. Therefore, wings enable flight.
  2. Insects generally survive mild winters better than harsh ones. Therefore, insect pests will become more problematic if global temperatures increase.
  3. Chromosomes, the carriers of DNA, are distributed evenly between the daughter cells during cell division. Therefore, each daughter cell will have the same chromosome set as the mother cell.
  4. Animals as diverse as humans, insects, and wolves all exhibit social behavior. Therefore, social behavior must have an evolutionary advantage.

The scientific method may seem too rigid and structured. It is important to keep in mind that, although scientists often follow this sequence, there is flexibility. Sometimes an experiment leads to conclusions that favor a change in approach. Often, an experiment brings entirely new scientific questions to the puzzle. Many times, science does not operate in a linear fashion. Instead, scientists continually draw inferences and make generalizations, finding patterns as their research proceeds. Scientific reasoning is more complex than the scientific method alone suggests. Notice, too, that we can apply the scientific method to solving problems that aren’t necessarily scientific in nature.

Two Types of Science: Basic Science and Applied Science

The scientific community has been debating for the last few decades about the value of different types of science. Is it valuable to pursue science for the sake of simply gaining knowledge, or does scientific knowledge only have worth if we can apply it to solving a specific problem or to bettering our lives? This question focuses on the differences between two types of science: basic science and applied science.

Basic science or “pure” science seeks to expand knowledge regardless of the short-term application of that knowledge. It is not focused on developing a product or a service of immediate public or commercial value. The immediate goal of basic science is knowledge for knowledge’s sake, although this does not mean that, in the end, it may not result in a practical application.

In contrast, applied science or “technology,” aims to use science to solve real-world problems, making it possible, for example, to improve a crop yield, find a cure for a particular disease, or save animals threatened by a natural disaster (Figure 1.8). In applied science, the problem is usually defined for the researcher.

Some individuals may perceive applied science as “useful” and basic science as “useless.” A question these people might pose to a scientist advocating knowledge acquisition would be, “What for?” However, a careful look at the history of science reveals that basic knowledge has resulted in many remarkable applications of great value. Many scientists think that a basic understanding of science is necessary before researchers develop an application, therefore, applied science relies on the results that researchers generate through basic science. Other scientists think that it is time to move on from basic science in order to find solutions to actual problems. Both approaches are valid. It is true that there are problems that demand immediate attention however, scientists would find few solutions without the help of the wide knowledge foundation that basic science generates.

One example of how basic and applied science can work together to solve practical problems occurred after the discovery of DNA structure led to an understanding of the molecular mechanisms governing DNA replication. DNA strands, unique in every human, are in our cells, where they provide the instructions necessary for life. When DNA replicates, it produces new copies of itself, shortly before a cell divides. Understanding DNA replication mechanisms enabled scientists to develop laboratory techniques that researchers now use to identify genetic diseases, pinpoint individuals who were at a crime scene, and determine paternity. Without basic science, it is unlikely that applied science could exist.

Another example of the link between basic and applied research is the Human Genome Project, a study in which researchers analyzed and mapped each human chromosome to determine the precise sequence of DNA subunits and each gene's exact location. (The gene is the basic unit of heredity represented by a specific DNA segment that codes for a functional molecule. An individual’s complete collection of genes is his or her genome.) Researchers have studied other less complex organisms as part of this project in order to gain a better understanding of human chromosomes. The Human Genome Project (Figure 1.9) relied on basic research with simple organisms and, later, with the human genome. An important end goal eventually became using the data for applied research, seeking cures and early diagnoses for genetically related diseases.

While scientists usually carefully plan research efforts in both basic science and applied science, note that some discoveries are made by serendipity , that is, by means of a fortunate accident or a lucky surprise. Scottish biologist Alexander Fleming discovered penicillin when he accidentally left a petri dish of Staphylococcus bacteria open. An unwanted mold grew on the dish, killing the bacteria. Fleming's curiosity to investigate the reason behind the bacterial death, followed by his experiments, led to the discovery of the antibiotic penicillin, which is produced by the fungus Penicillium. Even in the highly organized world of science, luck—when combined with an observant, curious mind—can lead to unexpected breakthroughs.

Reporting Scientific Work

Whether scientific research is basic science or applied science, scientists must share their findings in order for other researchers to expand and build upon their discoveries. Collaboration with other scientists—when planning, conducting, and analyzing results—is important for scientific research. For this reason, important aspects of a scientist’s work are communicating with peers and disseminating results to peers. Scientists can share results by presenting them at a scientific meeting or conference, but this approach can reach only the select few who are present. Instead, most scientists present their results in peer-reviewed manuscripts that are published in scientific journals. Peer-reviewed manuscripts are scientific papers that a scientist’s colleagues or peers review. These colleagues are qualified individuals, often experts in the same research area, who judge whether or not the scientist’s work is suitable for publication. The process of peer review helps to ensure that the research in a scientific paper or grant proposal is original, significant, logical, and thorough. Grant proposals, which are requests for research funding, are also subject to peer review. Scientists publish their work so other scientists can reproduce their experiments under similar or different conditions to expand on the findings.

A scientific paper is very different from creative writing. Although creativity is required to design experiments, there are fixed guidelines when it comes to presenting scientific results. First, scientific writing must be brief, concise, and accurate. A scientific paper needs to be succinct but detailed enough to allow peers to reproduce the experiments.

The scientific paper consists of several specific sections—introduction, materials and methods, results, and discussion. This structure is sometimes called the “IMRaD” format. There are usually acknowledgment and reference sections as well as an abstract (a concise summary) at the beginning of the paper. There might be additional sections depending on the type of paper and the journal where it will be published. For example, some review papers require an outline.

The introduction starts with brief, but broad, background information about what is known in the field. A good introduction also gives the rationale of the work. It justifies the work carried out and also briefly mentions the end of the paper, where the researcher will present the hypothesis or research question driving the research. The introduction refers to the published scientific work of others and therefore requires citations following the style of the journal. Using the work or ideas of others without proper citation is plagiarism .

The materials and methods section includes a complete and accurate description of the substances the researchers use, and the method and techniques they use to gather data. The description should be thorough enough to allow another researcher to repeat the experiment and obtain similar results, but it does not have to be verbose. This section will also include information on how the researchers made measurements and the types of calculations and statistical analyses they used to examine raw data. Although the materials and methods section gives an accurate description of the experiments, it does not discuss them.

Some journals require a results section followed by a discussion section, but it is more common to combine both. If the journal does not allow combining both sections, the results section simply narrates the findings without any further interpretation. The researchers present results with tables or graphs, but they do not present duplicate information. In the discussion section, the researchers will interpret the results, describe how variables may be related, and attempt to explain the observations. It is indispensable to conduct an extensive literature search to put the results in the context of previously published scientific research. Therefore, researchers include proper citations in this section as well.

Finally, the conclusion section summarizes the importance of the experimental findings. While the scientific paper almost certainly answers one or more scientific questions that the researchers stated, any good research should lead to more questions. Therefore, a well-done scientific paper allows the researchers and others to continue and expand on the findings.

Review articles do not follow the IMRAD format because they do not present original scientific findings, or primary literature. Instead, they summarize and comment on findings that were published as primary literature and typically include extensive reference sections.

News from Brown

Editors — The following release was updated July 21, 2014. The overall and annual numbers of filicides stated below reflect corrections made to the data in the research paper. The other figures remain accurate.

PROVIDENCE, R.I. [Brown University] — Instances in which parents kill their children may seem so horrifying and tragic that they defy explanation. Published scientific and medical research, meanwhile, doesn’t offer much epidemiological context to help people understand patterns among such heinous crimes. A paper in the March edition of the journal Forensic Science International provides the first comprehensive statistical analysis of filicide in the United States, drawing on 32 years of data on more than 15,000 arrests. The study also explores possible underlying psychiatric and biological underpinnings of filicide.

The research could help identify valid patterns among filicide cases, said lead author Dr. Timothy Mariano, a third-year psychiatry resident in the Alpert Medical School of Brown University, which could in turn aid in studying the causes of filicide.

“To know more about the epidemiology of this crime will hopefully help medical practitioners to identify people who are at risk for committing such crimes and that will help us with prevention, which is the ultimate goal of this research,” Mariano said.

A broad understanding of filicide, for instance, can help disabuse professionals and members of the public of certain myths and stereotypes about the crime, said senior author Dr. Wade Myers, professor of psychiatry and human behavior at Brown and a forensic psychiatrist at Rhode Island Hospital. For example, the data show that men are about as likely as women to kill infants. Stepchildren are not more likely than biological children to die at their parents’ hands, and nearly one in five filicides (18 percent) are killings of adult children, suggesting filicide is a lifetime risk.

About the updated figures
The total number of cases cited in the paper were derived from an analysis of the FBI raw data by Fox and Swatt (2008). Their analysis expanded the apparent number of cases in the data by creating five imputations of each original case in which they probabilistically tried to account for missing data. In our secondary analysis we failed to filter the data correctly, mistakenly counting the five imputed cases in addition to the original case, leading to an errant total of six times too many cases. None of the data interpretation, discussion, or conclusions of the study were affected.

Statistical context

The data in the study, first published online last month, come from the U.S. Federal Bureau of Investigation’s Supplementary Homicide Reports (SHR) database. Mariano, Myers, and co-author Heng Choon Chan looked at 632,017 arrests between 1976 and 2007, finding that 15,691 cases (2.5 percent) were filicides. The database includes information on the ages, genders, and races of the victims and alleged offenders, as well as the means employed to commit the murder.

Over time, the total number of cases in the country has remained relatively stable at around 500 a year. There may be some good news, however. Not only has the number drifted somewhat downward since the early 1990s, but also the numbers did not climb with population growth over the last three decades.

Close to three-quarters (72 percent) of the children killed were age 6 or younger. One-third were infants (children less than 1 year of age). Only about 10 percent of children killed were between ages 7 and 18. Adult offspring were the balance of the victims. Male children were more likely to be killed (58.3 percent) than female children. About 11 percent of victims were stepchildren, which is on the low end of the estimated proportion of U.S. children (10-20 percent) who live with a stepparent.

Among offenders, while fathers were about equally likely to kill an infant, they were more likely to be the alleged murderer of children older than a year, especially when the children were adults (fathers were the offenders in 78.3 percent of those cases). Overall, fathers were the accused murderer 57.4 percent of the time.

The data allowed the researchers to determine the most common filicide scenarios. A father killing a son was the most likely (29.5 percent of cases), a mother killing a son (22.1 percent) follows. A mother was slightly more likely to kill a daughter (19.7 percent of cases) than a father was (18.1 percent). The rarest instances were stepmothers killing either a stepson (0.5 percent) or a stepdaughter (0.3 percent).

The researchers found that the most common method of killing was with “personal weapons,” such as by the beating, choking, or drowning of victims. Parents used these means in 69 percent of murders of infants. As victims aged, firearms were more common, becoming the weapon used in 72.3 percent of the cases in which the victim as an adult. Men were much more likely to use guns than women. Across the board, parents rarely used contact weapons (such as a bat) or edged weapons (such as a knife). While stepparents weren’t overrepresented in the study, they were twice as likely as biological parents to use guns to (40 percent vs. 21 percent).

Biological underpinnings

Before Mariano worked with Myers and Chan to analyze the Supplementary Homicide Reports data, he had begun studying filicide while on a psychiatry rotation in medical school at Case Western Reserve University. There he had been reviewing the scientific literature on animal models of filicide. That published work, combined with studies of people and trends in the arrest statistics, offers a way for mental health professionals to develop hypotheses about the causes of filicide, he said.

In the current paper, Mariano synthesizes three main hypotheses about these underlying motives. One is that at least some parents who commit filicide have mental illness that derives from low levels of the neurotransmitter serotonin. Not only is that borne out in some animal studies, but the most typical ages of filicidal parents in the SHR data (18-30 years) are also the age at which many serotonin-related illnesses occur, like depression and schizophrenia.

Looking at the substantial differences that gender appears to make in the SHR data, a second hypothesis focuses on sex hormones. High levels of testosterone appear to coincide with higher rates of filicide in animal studies, for example, and in the crime statistics men were more likely to commit filicide, especially after victims were older than a year.

The final hypothetical motive category pertains mostly to those youngest of victims, “the unwanted child.” This evolutionarily motivated idea, also informed by other studies, suggests that parents, particularly young mothers, may kill young children who are sick or for whom they feel they cannot provide care.

Neither the statistics nor the hypotheses definitively explain filicide, but they provide researchers with a basis to focus their inquiries, Mariano and Myers said.

“Hopefully future research will continue to improve society’s ability to identify, manage, and treat populations at risk,” they conclude.

The research was partially funded by a grant from the National Institutes of Health (grant: T32GM007250).

Find a Specialist Find a Specialist

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources

  • To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by the American College of Medical Genetics and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from MedlinePlus Genetics.


Hyperbilirubinemia is more severe in newborns. Therefore precautionary measure should be adopted by both parents, and clinicians to diagnose and treat the disease properly. Government and public health organizations should arrange seminars, workshops and trainings for mothers regarding neonatal jaundice. Medical scientists should search for new treatments and preventive measures having no side effects and capable of recovering babies more speedily. Partners should screen their ABO blood groups as well as Rh factor before marriage. Consanguineous marriages should be avoided.

4. Some Comparable Cases

Some key details of this case are inspired by the case of Bengü Sezen and Dalibor Sames in the Chemistry Department at Columbia University. The press coverage of the case began, in 2006, with a set of retracted papers and a dispute between Sames, the senior author, and Sezen, his former graduate student, about whether the papers ought to have been retracted, as well as about whether the experiments reported in those papers were reproducible (Chang 2006a/b). By the time the findings of the United States Department of Health and Human Services on the matter were published in the Federal Register in 2010, Sezen had been found guilty of falsification, fabrication, and plagiarism of research data in three published papers and in her doctoral dissertation. As well, the investigation conducted at Columbia University found that Sames asked two graduate students who had devoted significant time and effort to attempts to replicate and extend Sezen’s work to leave his group (Schulz 2011).

There are other cases involving disputes about whether a finding is reproducible in which misconduct is suggested but not proven. An interesting example of this sort is the case of Duke University biochemist Homme W. Hellinga and his graduate student, Mary Dwyer, who coauthored, and then retracted, a pair of papers on enzymes designed using computational methods. According to news coverage around the retractions, Dwyer was concerned that her experimental results were too variable to be ready for publication, while Hellinga thought that the amount of variability they were seeing was normal for this type of system. (The published papers, however, failed to note this experimental variability.) When other researchers tried repeating these experiments and found no enzymatic activity from the designed enzymes, Hellinga at first assured them that the experiments worked, and that he knew this because the Hellinga lab had run a number of negative controls. Later, according to Dwyer, Hellinga confronted her and said "I find it really hard to believe that you didn’t make this up" (Hayden 2008, p. 277). Hellinga retracted the papers, but other researchers remained skeptical that the results reported in them could have been produced using the assays the papers described (Arnaud 2008, p. 41). An inquiry at Duke University cleared Dwyer of the allegations of falsification and fabrication of results. The Hellinga case raises a question that is also central to The Case of the Finicky Reactions, namely, how much responsibility does the senior researcher have for scientific work co-authored with his graduate student?

The differentials in experience and power between graduate students and principal investigators can complicate the kind of communication that is essential for knowledge-building. It is hard enough to share the news that one’s experimental efforts have been unsuccessful. It is even harder to confront one’s supervisor with concerns about misconduct. A number of real-world cases of scientific misconduct have come to light because graduate students or postdocs decided to be whistleblowers, reporting problems in their research groups so they could be addressed. Among these is the case of Diederik Stapel, a social psychologist forced to retract more that 50 publications because he fabricated the results that they reported. Some of his graduate students, concerned about what seemed to be anomalies in experimental results, asked Stapel if they could examine the raw data. When told he no longer had the raw data, they became suspicious but feared that reporting their suspicions would be damaging to their careers. Eventually, Stapel’s students were able to persuade his department chair that something was amiss, which ultimately led to Stapel’s dismissal (Bhattacharjee 2013).

Another case illustrates the high costs for students of blowing the whistle on an advisor’s misconduct. Students of Elizabeth Goodwin in the genetics department at the University of Wisconsin-Madison brought their concerns about experimental data and manipulated figures in Goodwin’s grant proposals to their department chair. This resulted in a university inquiry that found Goodwin had falsified data in proposals, after which Goodwin resigned her post. Of the six students who brought forward these concerns, three left the Ph.D. program without their degrees, and two others were starting over in new graduate programs, essentially losing the years that they had invested as students in Goodwin’s lab (Couzin 2006, p. 1222).

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Species are spread in space, whereas sampling is sparse. Thus, to describe and map along environmental gradients, it is necessary to interpolate the species abundance. Considering the plethora of valid methods, the researcher gets easily puzzled to choose the most appropriate interpolation approach with reference to the ecological question being asked.

We propose a procedure to select among alternative spatial distribution models and we illustrate it with 175 marine species distributions (35 species * 5 years). In a first step, the distribution of the variance explained by the predictive model (VEcv) given by 10-fold cross validation is estimated for each interpolation method. When the inter-quartile range of the VEcv distribution of the different methods overlap, the selection passes to a second step, using 11 measures belonging to three criteria: 1) error based measures, 2) spatial equivalence measures (center of gravity, inertia, isotropy and index of aggregation) and 3) measures based on the data integrity after interpolation, for example the percentage of area over the maximum sampled data.

We applied our approach to marine species sampled using either stratified random survey (trawl) or systematic survey (acoustic). We found that 87% of all species distributions had overlapping VEcv and thus passed the first selection. In the second selection step, the best method varied with species and year, although general additive model (GAM), Thin Plate Spline (TPS), Universal Kriging (UKr) and Random Forest (Rfor) performed better for the trawl data and TPS, Ordinary Kriging (OKri) and UKr for the acoustic data. Further, the results differed within methods (e.g. kriging neighborhood and type of kriging) and small modifications on the specifications can have a large impact on the surfaces produced.

The proposed approach 1) is accessible and intuitive, and does not require any complex software or sophisticated methodology 2) shows exactly in what aspects each interpolation model is prevalent over the others and permits to make a decision accordingly to the objectives of the study 3) takes into account different criteria to evaluate each, properties of an interpolation method 4) is universal and does not depend on the method used or the data characteristics. A detailed review on the subject is also included.

13.2 Review Questions

How do lungs work? – Emma Bryce, TED-Ed, 2014.

Why Do Men Have Deeper Voices? BrainStuff – HowStuffWorks, 2015.

Why does your voice change as you get older? – Shaylin A. Schundler, TED-Ed, 2018.

This article is published with permission of the Director of Kemri. CR Newton was funded by the Wellcome Trust UK . The authors would like to thank Nehemiah Kombo for transcribing the audio tapes and data management. We would like to thank all the participants for their time. We would like to thank the two anonymous reviewers for their insightful comments and suggestion.

Conceived and designed the experiments: AA AV RF CN. Performed the experiments: AA GB. Analyzed the data: AA JG. Wrote the paper: AA. Provided critical academic feedback revised and approved final draft: AV RF GB JG CN.

Watch the video: Complete Genomics Case Study (January 2023).