Science in the News Logo

SITNFlash

February 2004

Human Cloning & Brain Size

The SITNFlash monthly email series reports interesting developments in the world of biological and biomedical science. This issue focuses on two major scientific advances that were made recently:

  1. Cloning of human stem cells by researchers in Korea

  2. Advances made on the why humans have large brains

Scientists Clone Human Embryos

Researchers in South Korea have made a major advance in stem cell research by cloning human embryos and then growing stem cells from these embryos. The use of stem cells for research purposes is extremely controversial as there remains the potential to clone human beings (reproductive cloning). However, in therapeutic cloning, or cloning for medical purposes, embryos are grown for a few days in the laboratory, and then their stem cells are removed. Stem cells are extremely valuable as they have the potential to develop into almost any cell type in our bodies. In fact, the researchers' primary goal is to make human cells that are genetically identical to a patient, so that the cells can then be used for treating diseases such as diabetes and heart disease. With this technology, it is possible to generate cells that are genetically identical to each person, and will avoid the major complication of tissue rejection that often occurs after transplant surgeries. Tissue rejection happens when a patient's immune system doesn't recognize the implanted cells as the body's own, and consequently attacks the new cells that have been surgically added.

This research on human cloning was carried out by Drs. Woo Suk Hwang and Shin Yong Moon at the Seoul National University and was published February 13, in the journal Science. Their experiments have sparked the debate on stem cells and cloning world wide. Drs. Hwang and Moon are funded by the Korean government, large companies and private organizations. In the US, many restrictions are applied to research on stem cells, specifically because of the fear of reproductive cloning. People are divided over this heated topic, which raises a number of ethical questions:

1. Where does life begin?
2. Is an embryo the equivalent of an adult human being?
3. What measures can we take as a society to cure human disease?

Additional websites that might be helpful:

Follow the coverage on NY Times: http://www.nytimes.com
NIH Stem cell information: http://stemcells.nih.gov/index.asp
The Stem cell debate:http://www.cnn.com/SPECIALS/2001/stemcell/

Why is the human brain so big?

Why are humans endowed with such extraordinarily large brains? While we have learned a lot about ourselves by studying our primate ancestors, so far scientists have not been able to identify the genes that control brain size. Recent work by Dr. Bruce Lahn at the University of Chicago has identified that the ASPM gene is important in the evolution of human brain size. Comparing genes from many species including various primates, cow, sheep, cat and dog, the researchers identifies that ASPM has had extra evolutionary pressure to change and lead to larger brains. This calculation entails analysis of the changes in the gene's nucleotides (the basic elements of DNA) and the subsequent changes in amino acids (the building blocks of proteins). Interestingly, the rate of evolution of ASPM peaked between the evolution of humans from their closest primate ancestors. The estimated evolution rate reveals a dramatic tendency for "adaptive evolution" of brains over time.

The theory of adaptive evolution originates from work that Charles Darwin carried out in the Galapagos Islands in 1831, and published in The Origin of Species . Darwin observed that various populations of finches living on the islands had developed differences in beak size, shape and length, and that these differences could not be attributed solely to natural evolutionary trends. Because these characteristics seemed to allow birds to access food supplies more effectively (crack nuts, dig into the ground), Darwin hypothesized that there was a selective pressure on the birds to adapt to food availability on the island.

The exciting discovery of adaptive evolution of the brain suggests that large brains were actively selected for in human population. This finding sheds light on the extremely complex and controversial topic of human evolution. While the finding supports current theories of evolution, it also raises a number of scientific and ethical questions including:

What is the current evolutionary trend of ASPM in the human population?
What is the direct function of ASPM in the human brain?
Is there something that we could do as a population to increase the rate of evolution of this gene to benefit future generations? 
Can evidence that strongly supports the theory of human evolution be embraced by religious communities?

Online extras on adaptive evolution and the human brain:

BBC coverage of Dr. Lahn's work: http://news.bbc.co.uk/2/hi/health/3392143.stm
A website dedicated to evolution based on a television series produced by PBS: http://www.pbs.org/wgbh/evolution/
Online version of The Origin of Species by Charles Darwin: http://www.literature.org/authors/darwin-charles/the-origin-of-species/
Essays by Charles Darwin on evolution: http://pages.britishlibrary.net/charles.darwin/texts/foundations/foundations_fm.htm
The National Center on Science Education explains theories of evolution, how evolution shapes current understanding of human origins, and the many controversies surrounding human evolution: http://www.natcenscied.org/

Upcoming Longwood Seminars

Longwood Seminars at Harvard Medical School, in the heart of Boston's Longwood Medical Area, are free public educational events featuring the latest information from Harvard medical faculty.

All programs are held 5:30-7:00 pm at Harvard Medical School, New Research Building, 77 Avenue Louis Pasteur, Boston. Light snacks & beverages may be purchased at the adjacent Elements Cafe prior to each program. Online registration at http://www.hms.harvard.edu/longwood_seminars/.

The 2004 schedule:


©2004 The President and Fellows of Harvard University
All other trademarks are property of their respective holders.