There would have been big insects, and fish species in bodies of water if fish did not make the switch to land according to Joost Woltering of University of Geneva The Hindu reported Monday.
"In the forming limbs the HoxA and HoxD genes are switched on in two independent 'waves' the first making the proximal limb (arm/leg) and the second making the digits (toes/fingers)," said Woltering in an email The Hindu reported.
"For instance, there are genes that are expressed in the hand and in hair follicles, this fact doesn't make them homologous structures," Woltering told The Hindu. "Only if the underlying 'switches' that determine where a gene is expressed are homologous, the structures are homologous," Woltering told The Hindu. "In the forming limbs the HoxA and HoxD genes are switched on in two independent 'waves' the first making the proximal limb (arm/leg) and the second making the digits (toes/fingers)," Woltering told The Hindu in a statement.
Scientists examined genes found in fish and mammals or Hox genes The Hindu reported. Fish organisms had characteristics to grow limbs and move around before the species evolutionized. The study is printed in the Public Library of Science Biology journal.
"Identical expression patterns of the same gene(s) could in principle be established by non-homologous regulatory mechanisms so it might be very helpful to look at the regulatory details," Dr. Arkhat Abzhanov, an evolutionary biologist from Harvard University told The Hindu via e-mail.
Separate scientists previously studied the bones of Tiktaalik roseae a 375-million-year-old fish, which it found on Ellsmere Island in 2004 Live Science reported. The species has a flat head, and sharp teeth Live Science reported.
The species is a mix between a fish, and a crocodile. It also grew to nine feet or 2.7 meters Live Science reported. It also searched for food in freshwater Live Science reported.
Tiktaalik also had a boundless ball and socket hip joint attached to a versatile femur, similar to the thigh of a tetrapod, and capable of reaching below a species body Live Science reported.
